Merge pull request #785 from Konshin/documentation_fix

suppress documentation warnings

.gitignore

@@ -18,4 +18,4 @@ profile
 # Desktop Servies
 .DS_Store
 
-Carthage.build
+Carthage/Build

.travis.yml

@@ -1,5 +1,70 @@
 language: objective-c
-script: script/cibuild
+xcode_workspace: Mantle.xcworkspace
+git:
+  submodules: false
+before_install:
+  - git submodule update --init --recursive
+script:
+  - set -o pipefail
+  - xcodebuild $XCODE_ACTION
+      -workspace "$TRAVIS_XCODE_WORKSPACE"
+      -scheme "$TRAVIS_XCODE_SCHEME"
+      -sdk "$XCODE_SDK"
+      -destination "$XCODE_DESTINATION"
+      RUN_CLANG_STATIC_ANALYZER=NO
+      | xcpretty
+matrix:
+  include:
+    # Xcode 8
+    - xcode_scheme: "Mantle Mac"
+      osx_image: xcode8.3
+      env:
+        - XCODE_ACTION=test
+        - XCODE_SDK=macosx
+        - XCODE_DESTINATION="arch=x86_64"
+    - xcode_scheme: "Mantle iOS"
+      osx_image: xcode8.3
+      env:
+        - XCODE_ACTION=test
+        - XCODE_SDK=iphonesimulator
+        - XCODE_DESTINATION="name=iPhone 7"
+    - xcode_scheme: "Mantle-tvOS"
+      osx_image: xcode8.3
+      env:
+        - XCODE_ACTION=test
+        - XCODE_SDK=appletvsimulator
+        - XCODE_DESTINATION="name=Apple TV 1080p"
+    - xcode_scheme: "Mantle-watchOS"
+      osx_image: xcode8.3
+      env:
+        - XCODE_ACTION=build
+        - XCODE_SDK=watchsimulator
+        - XCODE_DESTINATION="name=Apple Watch - 38mm"
+    # Xcode 9
+    - xcode_scheme: "Mantle Mac"
+      osx_image: xcode9
+      env:
+        - XCODE_ACTION=test
+        - XCODE_SDK=macosx
+        - XCODE_DESTINATION="arch=x86_64"
+    - xcode_scheme: "Mantle iOS"
+      osx_image: xcode9
+      env:
+        - XCODE_ACTION=test
+        - XCODE_SDK=iphonesimulator
+        - XCODE_DESTINATION="name=iPhone 7"
+    - xcode_scheme: "Mantle-tvOS"
+      osx_image: xcode9
+      env:
+        - XCODE_ACTION=test
+        - XCODE_SDK=appletvsimulator
+        - XCODE_DESTINATION="name=Apple TV 1080p"
+    - xcode_scheme: "Mantle-watchOS"
+      osx_image: xcode9
+      env:
+        - XCODE_ACTION=build
+        - XCODE_SDK=watchsimulator
+        - XCODE_DESTINATION="name=Apple Watch - 38mm"
 notifications:
   email: false
   campfire:

CHANGELOG.md

@@ -0,0 +1,188 @@
+# 2.0
+
+This release of Mantle contains major breaking changes that we were unable to
+make after freezing the 1.0 API.
+
+The changes in 2.0 focus on simplifying concepts and increasing flexibility in
+the framework.
+
+For a complete list of the changes made in Mantle 2.0, see [the
+milestone](https://github.com/Mantle/Mantle/issues?q=milestone%3A2.0+is%3Aclosed).
+
+**[Breaking changes](#breaking-changes)**
+
+ 1. [Explicit JSON key paths](#explicit-json-key-paths)
+ 1. [Predefined transformers now part of JSON adapter](#predefined-transformers-now-part-of-json-adapter)
+ 1. [Core Data adapter now separate](#core-data-adapter-now-separate)
+ 1. [Managed object transformers reversed](#managed-object-transformers-reversed)
+ 1. [OS X 10.9 and iOS 8](#os-x-109-and-ios-8)
+ 1. [JSON key paths can only traverse objects](#json-key-paths-can-only-traverse-objects)
+
+**[Additions and improvements](#additions-and-improvements)**
+
+ 1. [MTLModel protocol](#mtlmodel-protocol)
+ 1. [Error handling for value transformers](#error-handling-for-value-transformers)
+ 1. [Storage behaviors for properties](#storage-behaviors-for-properties)
+ 1. [Type checking during JSON parsing](#type-checking-during-json-parsing)
+ 1. [Mapping multiple JSON fields to a single property](#mapping-multiple-json-fields-to-a-single-property)
+
+## Breaking changes
+
+### Explicit JSON key paths
+
+`+JSONKeyPathsByPropertyKey` will [no
+longer](https://github.com/Mantle/Mantle/pull/170) infer your property mappings
+automatically.
+
+Instead, you must explicitly specify every property that should
+be mapped, and any properties omitted will not be considered for JSON
+serialization or deserialization.
+
+For convenience, you can use `+[NSDictionary mtl_identityPropertyMapWithModel:]`
+to automatically create a one-to-one mapping that matches the previous default
+behavior.
+
+**To update:**
+
+ * Explicitly declare any property mappings in `+JSONKeyPathsByPropertyKey`
+   that were previously implicit.
+ * Optionally use `+[NSDictionary mtl_identityPropertyMapWithModel:]` for an
+   initial property map.
+
+### Predefined transformers now part of JSON adapter
+
+The `+mtl_JSONDictionaryTransformerWithModelClass:` and
+`+mtl_JSONArrayWithModelClass:` methods [have
+moved](https://github.com/Mantle/Mantle/pull/474) to `MTLJSONAdapter`.
+
+This allows custom JSON adapter subclasses to substitute their own transformers
+with additional logic, and moves the transformers closer to their actual point
+of use.
+
+**To update:**
+
+ * Replace occurrences of `+[NSValueTransformer
+   mtl_JSONDictionaryTransformerWithModelClass:]` with `+[MTLJSONAdapter
+   dictionaryTransformerWithModelClass:]`
+ * Replace occurrences of `+[NSValueTransformer
+   mtl_JSONArrayTransformerWithModelClass:]` with `+[MTLJSONAdapter
+   arrayTransformerWithModelClass:]`
+
+### Core Data adapter now separate
+
+The `MTLManagedObjectAdapter` class, used for converting to and from Core Data
+objects, has been moved to [its own
+framework](https://github.com/Mantle/MTLManagedObjectAdapter). This better
+indicates its “semi-official” status, as it gets less attention than the core
+Mantle features.
+
+**To update:**
+
+ * Import the
+   [MTLManagedObjectAdapter](https://github.com/Mantle/MTLManagedObjectAdapter)
+   framework into your project.
+
+### Managed object transformers reversed
+
+In addition to being [a separate framework](#core-data-adapter-now-separate),
+the behavior of `MTLManagedObjectAdapter` has changed as well—specifically, the
+direction of managed object attribute transformers has been flipped.
+
+Managed object transformers now convert _from_ managed object attributes _to_
+model properties in the forward direction. In the reverse direction, they
+convert from properties to managed object attributes.
+
+**To update:**
+
+ * Swap the forward and reverse transformation logic of any custom managed
+   object transformers, or use `-mtl_invertedTransformer` to do it
+   automatically.
+
+### OS X 10.9 and iOS 8
+
+Mantle now requires OS X 10.9+ or iOS 8+, for the use of Swift and dynamic
+frameworks.
+
+**To update:**
+
+ * Increase your project’s deployment target to at least OS X 10.9 or iOS 8.
+
+### JSON key paths can only traverse objects
+
+Every element of a JSON key path specified in `+JSONKeyPathsByPropertyKey` [must
+now refer to an object](https://github.com/Mantle/Mantle/pull/275) (dictionary).
+
+It was [previously possible](https://github.com/Mantle/Mantle/issues/257) to use
+an array as a key path element, but this was unintended behavior, and is now
+explicitly disallowed.
+
+**To update:**
+
+ * If you were using an array as an element in a key path, change the key path
+   to end at the array, and [update your JSON transformer](https://github.com/Mantle/Mantle/issues/257#issuecomment-36846503)
+   to handle the nested elements instead.
+
+## Additions and improvements
+
+### MTLModel protocol
+
+The [new `<MTLModel>` protocol](https://github.com/Mantle/Mantle/pull/219) represents the basic behaviors expected from any
+model object, and can be used instead of the `MTLModel` class when inheritance
+is impossible, or to create more generic APIs.
+
+For example, `<MTLModel>` conformance can be added to the objects from other
+persistence frameworks in order to use those objects in conjunction with
+Mantle’s adapters.
+
+Accordingly, `MTLJSONAdapter` has been updated to only depend on `<MTLModel>`
+conformance, and no longer requires a `MTLModel` subclass in order to serialize
+or deserialize from JSON.
+
+### Error handling for value transformers
+
+The [new `<MTLTransformerErrorHandling>`
+protocol](https://github.com/Mantle/Mantle/pull/153) can be used to add error
+reporting behaviors to any `NSValueTransformer`.
+
+`MTLValueTransformer` has been updated to take advantage of the new interface,
+with the following new methods that provide error information:
+
+ * `+transformerUsingForwardBlock:`
+ * `+transformerUsingReversibleBlock:`
+ * `+transformerUsingForwardBlock:reverseBlock:`
+
+Similarly, the predefined transformers that Mantle provides now provide error
+information upon failure as well.
+
+### Storage behaviors for properties
+
+The [new `+storageBehaviorForPropertyWithKey:`
+method](https://github.com/Mantle/Mantle/pull/210) can be used to redefine the
+default behavior of methods like `-dictionaryValue`, `-isEqual:`,
+`-description`, and `-copy` all at once.
+
+Properties which have been omitted from `+propertyKeys` by default will continue
+to be omitted under the new API, with a default behavior of
+`MTLPropertyStorageNone`.
+
+### Type checking during JSON parsing
+
+`MTLJSONAdapter` now [implicitly
+validates](https://github.com/Mantle/Mantle/pull/251) the type of values
+assigned to your `<MTLModel>` objects during JSON parsing.
+
+This can be prevent errors like an `NSString` being assigned to a `BOOL`
+property.
+
+This is only a simple safety check, though, and cannot catch every kind of
+error! Continue to verify that your types align ahead of time.
+
+### Mapping multiple JSON fields to a single property
+
+`MTLJSONAdapter` can now map multiple fields to a single property, and 
+vice-versa. Specify an array of keypaths for the property when implementing 
+`+JSONKeyPathsByPropertyKey` rather than an `NSString`.
+
+The default behaviour is to set the property to a dictionary of values for the 
+specified keypaths. If you specify a value transformer for the given property 
+key, this transformer will receive an `NSDictionary` of values.

Cartfile.private

@@ -1,3 +1,3 @@
-github "jspahrsummers/xcconfigs" >= 0.8
-github "Quick/Quick" ~> 0.2
-github "Quick/Nimble" ~> 0.2
+github "jspahrsummers/xcconfigs" "1ef9763"
+github "Quick/Quick" ~> 1.1.0
+github "Quick/Nimble" ~> 7.0.1

Cartfile.resolved

@@ -1,3 +1,3 @@
-github "Quick/Nimble" "v0.2.0"
-github "Quick/Quick" "v0.2.3"
-github "jspahrsummers/xcconfigs" "0.8.1"
+github "Quick/Nimble" "v7.0.1"
+github "Quick/Quick" "v1.1.0"
+github "jspahrsummers/xcconfigs" "1ef97639ffbe041da0b1392b2114fa19b922a7a1"

Carthage/Checkouts/Nimble

@@ -1 +1 @@
-Subproject commit 6f787eeb75b2fa71464981f28b3dc8d7bd532e69
+Subproject commit 39b67002306fda9de4c9fd1290a6295f97edd09e

Carthage/Checkouts/Quick

@@ -1 +1 @@
-Subproject commit ce729620fa9db8d3c76b69bbfc429cece97dbe36
+Subproject commit e4fa1e85c0305ba4e0866f25812d3fa398f3a048

Carthage/Checkouts/xcconfigs

@@ -1 +1 @@
-Subproject commit 99624a6af366c015b678a1135e4c558776a59be6
+Subproject commit 1ef97639ffbe041da0b1392b2114fa19b922a7a1

LICENSE.md

@@ -1,4 +1,4 @@
-**Copyright (c) 2012 - 2014, GitHub, Inc.**
+**Copyright (c) GitHub, Inc.**
 **All rights reserved.**
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

Mantle.xcodeproj/xcshareddata/xcschemes/Mantle Mac.xcscheme

@@ -1,10 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0620"
+   LastUpgradeVersion = "0800"
    version = "2.0">
    <BuildAction
-      parallelizeBuildables = "YES"
-      buildImplicitDependencies = "YES">
+      parallelizeBuildables = "NO"
+      buildImplicitDependencies = "NO">
       <BuildActionEntries>
          <BuildActionEntry
             buildForTesting = "YES"
@@ -20,6 +20,34 @@
                ReferencedContainer = "container:Mantle.xcodeproj">
             </BuildableReference>
          </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "1F925EAC195C0D6300ED456B"
+               BuildableName = "Nimble.framework"
+               BlueprintName = "Nimble-macOS"
+               ReferencedContainer = "container:Carthage/Checkouts/Nimble/Nimble.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "DAEB6B8D1943873100289F44"
+               BuildableName = "Quick.framework"
+               BlueprintName = "Quick-macOS"
+               ReferencedContainer = "container:Carthage/Checkouts/Quick/Quick.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
          <BuildActionEntry
             buildForTesting = "YES"
             buildForRunning = "NO"
@@ -37,10 +65,10 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
+      buildConfiguration = "Release"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      shouldUseLaunchSchemeArgsEnv = "YES"
-      buildConfiguration = "Release">
+      shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
          <TestableReference
             skipped = "NO">
@@ -62,16 +90,19 @@
             ReferencedContainer = "container:Mantle.xcodeproj">
          </BuildableReference>
       </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
    </TestAction>
    <LaunchAction
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = ""
       selectedLauncherIdentifier = "Xcode.IDEFoundation.Launcher.PosixSpawn"
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
-      buildConfiguration = "Debug"
       ignoresPersistentStateOnLaunch = "NO"
       debugDocumentVersioning = "YES"
       debugXPCServices = "NO"
+      debugServiceExtension = "internal"
       allowLocationSimulation = "YES">
       <MacroExpansion>
          <BuildableReference
@@ -86,10 +117,10 @@
       </AdditionalOptions>
    </LaunchAction>
    <ProfileAction
+      buildConfiguration = "Profile"
       shouldUseLaunchSchemeArgsEnv = "YES"
       savedToolIdentifier = ""
       useCustomWorkingDirectory = "NO"
-      buildConfiguration = "Profile"
       debugDocumentVersioning = "YES">
       <MacroExpansion>
          <BuildableReference

Mantle.xcodeproj/xcshareddata/xcschemes/Mantle iOS.xcscheme

@@ -1,10 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0620"
+   LastUpgradeVersion = "0800"
    version = "1.3">
    <BuildAction
-      parallelizeBuildables = "YES"
-      buildImplicitDependencies = "YES">
+      parallelizeBuildables = "NO"
+      buildImplicitDependencies = "NO">
       <BuildActionEntries>
          <BuildActionEntry
             buildForTesting = "YES"
@@ -20,6 +20,34 @@
                ReferencedContainer = "container:Mantle.xcodeproj">
             </BuildableReference>
          </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "1F1A74281940169200FFFC47"
+               BuildableName = "Nimble.framework"
+               BlueprintName = "Nimble-iOS"
+               ReferencedContainer = "container:Carthage/Checkouts/Nimble/Nimble.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "5A5D117B19473F2100F6D13D"
+               BuildableName = "Quick.framework"
+               BlueprintName = "Quick-iOS"
+               ReferencedContainer = "container:Carthage/Checkouts/Quick/Quick.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
          <BuildActionEntry
             buildForTesting = "YES"
             buildForRunning = "NO"
@@ -37,10 +65,10 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      shouldUseLaunchSchemeArgsEnv = "YES"
-      buildConfiguration = "Debug">
+      shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
          <TestableReference
             skipped = "NO">
@@ -62,15 +90,18 @@
             ReferencedContainer = "container:Mantle.xcodeproj">
          </BuildableReference>
       </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
    </TestAction>
    <LaunchAction
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
-      buildConfiguration = "Debug"
       ignoresPersistentStateOnLaunch = "NO"
       debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
       allowLocationSimulation = "YES">
       <MacroExpansion>
          <BuildableReference
@@ -85,10 +116,10 @@
       </AdditionalOptions>
    </LaunchAction>
    <ProfileAction
+      buildConfiguration = "Release"
       shouldUseLaunchSchemeArgsEnv = "YES"
       savedToolIdentifier = ""
       useCustomWorkingDirectory = "NO"
-      buildConfiguration = "Release"
       debugDocumentVersioning = "YES">
       <MacroExpansion>
          <BuildableReference

Mantle.xcodeproj/xcshareddata/xcschemes/Mantle-tvOS.xcscheme

@@ -0,0 +1,141 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "0800"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "NO"
+      buildImplicitDependencies = "NO">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "CDEEABA71D33FC5100240A4B"
+               BuildableName = "Mantle.framework"
+               BlueprintName = "Mantle-tvOS"
+               ReferencedContainer = "container:Mantle.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "1F5DF1541BDCA0CE00C3A531"
+               BuildableName = "Nimble.framework"
+               BlueprintName = "Nimble-tvOS"
+               ReferencedContainer = "container:Carthage/Checkouts/Nimble/Nimble.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "1F118CD41BDCA4AB005013A2"
+               BuildableName = "Quick.framework"
+               BlueprintName = "Quick-tvOS"
+               ReferencedContainer = "container:Carthage/Checkouts/Quick/Quick.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "CDEEABD31D33FC7900240A4B"
+               BuildableName = "Mantle-tvOSTests.xctest"
+               BlueprintName = "Mantle-tvOSTests"
+               ReferencedContainer = "container:Mantle.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "CDEEABD31D33FC7900240A4B"
+               BuildableName = "Mantle-tvOSTests.xctest"
+               BlueprintName = "Mantle-tvOSTests"
+               ReferencedContainer = "container:Mantle.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "CDEEABA71D33FC5100240A4B"
+            BuildableName = "Mantle.framework"
+            BlueprintName = "Mantle-tvOS"
+            ReferencedContainer = "container:Mantle.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "CDEEABA71D33FC5100240A4B"
+            BuildableName = "Mantle.framework"
+            BlueprintName = "Mantle-tvOS"
+            ReferencedContainer = "container:Mantle.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "CDEEABA71D33FC5100240A4B"
+            BuildableName = "Mantle.framework"
+            BlueprintName = "Mantle-tvOS"
+            ReferencedContainer = "container:Mantle.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

Mantle.xcodeproj/xcshareddata/xcschemes/Mantle-watchOS.xcscheme

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "0800"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "NO"
+      buildImplicitDependencies = "NO">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "CD7C6D881D33ACCC002EC294"
+               BuildableName = "Mantle.framework"
+               BlueprintName = "Mantle-watchOS"
+               ReferencedContainer = "container:Mantle.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+      </Testables>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "CD7C6D881D33ACCC002EC294"
+            BuildableName = "Mantle.framework"
+            BlueprintName = "Mantle-watchOS"
+            ReferencedContainer = "container:Mantle.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "CD7C6D881D33ACCC002EC294"
+            BuildableName = "Mantle.framework"
+            BlueprintName = "Mantle-watchOS"
+            ReferencedContainer = "container:Mantle.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

Mantle/Info.plist

@@ -7,7 +7,7 @@
 	<key>CFBundleExecutable</key>
 	<string>$(EXECUTABLE_NAME)</string>
 	<key>CFBundleIdentifier</key>
-	<string>org.mantle.$(PRODUCT_NAME:rfc1034identifier)</string>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
 	<key>CFBundleInfoDictionaryVersion</key>
 	<string>6.0</string>
 	<key>CFBundleName</key>

Mantle/MTLJSONAdapter.h

@@ -8,165 +8,280 @@
 
 #import <Foundation/Foundation.h>
 
-@class MTLModel;
+@protocol MTLModel;
+@protocol MTLTransformerErrorHandling;
 
-// A MTLModel object that supports being parsed from and serialized to JSON.
-@protocol MTLJSONSerializing
+/// A MTLModel object that supports being parsed from and serialized to JSON.
+@protocol MTLJSONSerializing <MTLModel>
 @required
 
-// Specifies how to map property keys to different key paths in JSON.
-//
-// Subclasses overriding this method should combine their values with those of
-// `super`.
-//
-// Any property keys not present in the dictionary are assumed to match the JSON
-// key that should be used. Any keys associated with NSNull will not participate
-// in JSON serialization.
-//
-// Returns a dictionary mapping property keys to JSON key paths (as strings) or
-// NSNull values.
+/// Specifies how to map property keys to different key paths in JSON.
+///
+/// Subclasses overriding this method should combine their values with those of
+/// `super`.
+///
+/// Values in the dictionary can either be key paths in the JSON representation
+/// of the receiver or an array of such key paths. If an array is used, the
+/// deserialized value will be a dictionary containing all of the keys in the
+/// array.
+///
+/// Any keys omitted will not participate in JSON serialization.
+///
+/// Examples
+///
+///     + (NSDictionary *)JSONKeyPathsByPropertyKey {
+///         return @{
+///             @"name": @"POI.name",
+///             @"point": @[ @"latitude", @"longitude" ],
+///             @"starred": @"starred"
+///         };
+///     }
+///
+/// This will map the `starred` property to `JSONDictionary[@"starred"]`, `name`
+/// to `JSONDictionary[@"POI"][@"name"]` and `point` to a dictionary equivalent
+/// to:
+///
+///     @{
+///         @"latitude": JSONDictionary[@"latitude"],
+///         @"longitude": JSONDictionary[@"longitude"]
+///     }
+///
+/// Returns a dictionary mapping property keys to one or multiple JSON key paths
+/// (as strings or arrays of strings).
 + (NSDictionary *)JSONKeyPathsByPropertyKey;
 
 @optional
 
-// Specifies how to convert a JSON value to the given property key. If
-// reversible, the transformer will also be used to convert the property value
-// back to JSON.
-//
-// If the receiver implements a `+<key>JSONTransformer` method, MTLJSONAdapter
-// will use the result of that method instead.
-//
-// Returns a value transformer, or nil if no transformation should be performed.
+/// Specifies how to convert a JSON value to the given property key. If
+/// reversible, the transformer will also be used to convert the property value
+/// back to JSON.
+///
+/// If the receiver implements a `+<key>JSONTransformer` method, MTLJSONAdapter
+/// will use the result of that method instead.
+///
+/// Returns a value transformer, or nil if no transformation should be performed.
 + (NSValueTransformer *)JSONTransformerForKey:(NSString *)key;
 
-// Overridden to parse the receiver as a different class, based on information
-// in the provided dictionary.
-//
-// This is mostly useful for class clusters, where the abstract base class would
-// be passed into -[MTLJSONAdapter initWithJSONDictionary:modelClass:], but
-// a subclass should be instantiated instead.
-//
-// JSONDictionary - The JSON dictionary that will be parsed.
-//
-// Returns the class that should be parsed (which may be the receiver), or nil
-// to abort parsing (e.g., if the data is invalid).
+/// Overridden to parse the receiver as a different class, based on information
+/// in the provided dictionary.
+///
+/// This is mostly useful for class clusters, where the abstract base class would
+/// be passed into -[MTLJSONAdapter initWithJSONDictionary:modelClass:], but
+/// a subclass should be instantiated instead.
+///
+/// JSONDictionary - The JSON dictionary that will be parsed.
+///
+/// Returns the class that should be parsed (which may be the receiver), or nil
+/// to abort parsing (e.g., if the data is invalid).
 + (Class)classForParsingJSONDictionary:(NSDictionary *)JSONDictionary;
 
 @end
 
-// The domain for errors originating from MTLJSONAdapter.
+/// The domain for errors originating from MTLJSONAdapter.
 extern NSString * const MTLJSONAdapterErrorDomain;
 
-// +classForParsingJSONDictionary: returned nil for the given dictionary.
+/// +classForParsingJSONDictionary: returned nil for the given dictionary.
 extern const NSInteger MTLJSONAdapterErrorNoClassFound;
 
-// The provided JSONDictionary is not valid.
+/// The provided JSONDictionary is not valid.
 extern const NSInteger MTLJSONAdapterErrorInvalidJSONDictionary;
 
-// The model's implementation of +JSONKeyPathsByPropertyKey included a key which
-// does not actually exist in +propertyKeys.
+/// The model's implementation of +JSONKeyPathsByPropertyKey included a key which
+/// does not actually exist in +propertyKeys.
 extern const NSInteger MTLJSONAdapterErrorInvalidJSONMapping;
 
-// Converts a MTLModel object to and from a JSON dictionary.
+/// An exception was thrown and caught.
+extern const NSInteger MTLJSONAdapterErrorExceptionThrown;
+
+/// Associated with the NSException that was caught.
+extern NSString * const MTLJSONAdapterThrownExceptionErrorKey;
+
+/// Converts a MTLModel object to and from a JSON dictionary.
 @interface MTLJSONAdapter : NSObject
 
-// The model object that the receiver was initialized with, or that the receiver
-// parsed from a JSON dictionary.
-@property (nonatomic, strong, readonly) MTLModel<MTLJSONSerializing> *model;
-
-// Attempts to parse a JSON dictionary into a model object.
-//
-// modelClass     - The MTLModel subclass to attempt to parse from the JSON.
-//                  This class must conform to <MTLJSONSerializing>. This
-//                  argument must not be nil.
-// JSONDictionary - A dictionary representing JSON data. This should match the
-//                  format returned by NSJSONSerialization. If this argument is
-//                  nil, the method returns nil.
-// error          - If not NULL, this may be set to an error that occurs during
-//                  parsing or initializing an instance of `modelClass`.
-//
-// Returns an instance of `modelClass` upon success, or nil if a parsing error
-// occurred.
+/// Attempts to parse a JSON dictionary into a model object.
+///
+/// modelClass     - The MTLModel subclass to attempt to parse from the JSON.
+///                  This class must conform to <MTLJSONSerializing>. This
+///                  argument must not be nil.
+/// JSONDictionary - A dictionary representing JSON data. This should match the
+///                  format returned by NSJSONSerialization. If this argument is
+///                  nil, the method returns nil.
+/// error          - If not NULL, this may be set to an error that occurs during
+///                  parsing or initializing an instance of `modelClass`.
+///
+/// Returns an instance of `modelClass` upon success, or nil if a parsing error
+/// occurred.
 + (id)modelOfClass:(Class)modelClass fromJSONDictionary:(NSDictionary *)JSONDictionary error:(NSError **)error;
 
-// Attempts to parse an array of JSON dictionary objects into a model objects
-// of a specific class.
-//
-// modelClass - The MTLModel subclass to attempt to parse from the JSON. This
-//              class must conform to <MTLJSONSerializing>. This argument must
-//              not be nil.
-// JSONArray  - A array of dictionaries representing JSON data. This should
-//              match the format returned by NSJSONSerialization. If this
-//              argument is nil, the method returns nil.
-// error      - If not NULL, this may be set to an error that occurs during
-//              parsing or initializing an any of the instances of
-//              `modelClass`.
-//
-// Returns an array of `modelClass` instances upon success, or nil if a parsing
-// error occurred.
+/// Attempts to parse an array of JSON dictionary objects into a model objects
+/// of a specific class.
+///
+/// modelClass - The MTLModel subclass to attempt to parse from the JSON. This
+///              class must conform to <MTLJSONSerializing>. This argument must
+///              not be nil.
+/// JSONArray  - A array of dictionaries representing JSON data. This should
+///              match the format returned by NSJSONSerialization. If this
+///              argument is nil, the method returns nil.
+/// error      - If not NULL, this may be set to an error that occurs during
+///              parsing or initializing an any of the instances of
+///              `modelClass`.
+///
+/// Returns an array of `modelClass` instances upon success, or nil if a parsing
+/// error occurred.
 + (NSArray *)modelsOfClass:(Class)modelClass fromJSONArray:(NSArray *)JSONArray error:(NSError **)error;
 
-// Converts a model into a JSON representation.
-//
-// model - The model to use for JSON serialization. This argument must not be
-//         nil.
-//
-// Returns a JSON dictionary, or nil if a serialization error occurred.
-+ (NSDictionary *)JSONDictionaryFromModel:(MTLModel<MTLJSONSerializing> *)model;
+/// Converts a model into a JSON representation.
+///
+/// model - The model to use for JSON serialization. This argument must not be
+///         nil.
+/// error - If not NULL, this may be set to an error that occurs during
+///         serializing.
+///
+/// Returns a JSON dictionary, or nil if a serialization error occurred.
++ (NSDictionary *)JSONDictionaryFromModel:(id<MTLJSONSerializing>)model error:(NSError **)error;
 
-// Converts a array of models into a JSON representation.
-//
-// models - The array of models to use for JSON serialization. This argument
-//          must not be nil.
-//
-// Returns a JSON array, or nil if a serialization error occurred for any
-// model.
-+ (NSArray *)JSONArrayFromModels:(NSArray *)models;
+/// Converts a array of models into a JSON representation.
+///
+/// models - The array of models to use for JSON serialization. This argument
+///          must not be nil.
+/// error  - If not NULL, this may be set to an error that occurs during
+///          serializing.
+///
+/// Returns a JSON array, or nil if a serialization error occurred for any
+/// model.
++ (NSArray *)JSONArrayFromModels:(NSArray *)models error:(NSError **)error;
 
-// Initializes the receiver by attempting to parse a JSON dictionary into
-// a model object.
-//
-// JSONDictionary - A dictionary representing JSON data. This should match the
-//                  format returned by NSJSONSerialization. If this argument is
-//                  nil, the method returns nil and an error with code
-//                  MTLJSONAdapterErrorInvalidJSONDictionary.
-// modelClass     - The MTLModel subclass to attempt to parse from the JSON.
-//                  This class must conform to <MTLJSONSerializing>. This
-//                  argument must not be nil.
-// error          - If not NULL, this may be set to an error that occurs during
-//                  parsing or initializing an instance of `modelClass`.
-//
-// Returns an initialized adapter upon success, or nil if a parsing error
-// occurred.
-- (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)modelClass error:(NSError **)error;
+/// Initializes the receiver with a given model class.
+///
+/// modelClass - The MTLModel subclass to attempt to parse from the JSON and
+///              back. This class must conform to <MTLJSONSerializing>. This
+///              argument must not be nil.
+///
+/// Returns an initialized adapter.
+- (id)initWithModelClass:(Class)modelClass;
 
-// Initializes the receiver with an existing model.
-//
-// model - The model to use for JSON serialization. This argument must not be
-//         nil.
-- (id)initWithModel:(MTLModel<MTLJSONSerializing> *)model;
+/// Deserializes a model from a JSON dictionary.
+///
+/// The adapter will call -validate: on the model and consider it an error if the
+/// validation fails.
+///
+/// JSONDictionary - A dictionary representing JSON data. This should match the
+///                  format returned by NSJSONSerialization. This argument must
+///                  not be nil.
+/// error          - If not NULL, this may be set to an error that occurs during
+///                  deserializing or validation.
+///
+/// Returns a model object, or nil if a deserialization error occurred or the
+/// model did not validate successfully.
+- (id)modelFromJSONDictionary:(NSDictionary *)JSONDictionary error:(NSError **)error;
 
-// Serializes the receiver's `model` into JSON.
-//
-// Returns a JSON dictionary, or nil if a serialization error occurred.
-- (NSDictionary *)JSONDictionary;
+/// Serializes a model into JSON.
+///
+/// model - The model to use for JSON serialization. This argument must not be
+///         nil.
+/// error - If not NULL, this may be set to an error that occurs during
+///         serializing.
+///
+/// Returns a model object, or nil if a serialization error occurred.
+- (NSDictionary *)JSONDictionaryFromModel:(id<MTLJSONSerializing>)model error:(NSError **)error;
 
-// Looks up the JSON key path in the model's +propertyKeys.
-//
-// Subclasses may override this method to customize the adapter's seralizing
-// behavior. You should not call this method directly.
-//
-// key - The property key to retrieve the corresponding JSON key path for. This
-//       argument must not be nil.
-//
-// Returns a key path to use, or nil to omit the property from JSON.
-- (NSString *)JSONKeyPathForPropertyKey:(NSString *)key;
+/// Filters the property keys used to serialize a given model.
+///
+/// propertyKeys - The property keys for which `model` provides a mapping.
+/// model        - The model being serialized.
+///
+/// Subclasses may override this method to determine which property keys should
+/// be used when serializing `model`. For instance, this method can be used to
+/// create more efficient updates of server-side resources.
+///
+/// The default implementation simply returns `propertyKeys`.
+///
+/// Returns a subset of propertyKeys that should be serialized for a given
+/// model.
+- (NSSet *)serializablePropertyKeys:(NSSet *)propertyKeys forModel:(id<MTLJSONSerializing>)model;
+
+/// An optional value transformer that should be used for properties of the given
+/// class.
+///
+/// A value transformer returned by the model's +JSONTransformerForKey: method
+/// is given precedence over the one returned by this method.
+///
+/// The default implementation invokes `+<class>JSONTransformer` on the
+/// receiver if it's implemented. It supports NSURL conversion through
+/// +NSURLJSONTransformer.
+///
+/// modelClass - The class of the property to serialize. This property must not be
+///              nil.
+///
+/// Returns a value transformer or nil if no transformation should be used.
++ (NSValueTransformer *)transformerForModelPropertiesOfClass:(Class)modelClass;
+
+/// A value transformer that should be used for a properties of the given
+/// primitive type.
+///
+/// If `objCType` matches @‎encode(id), the value transformer returned by
+/// +transformerForModelPropertiesOfClass: is used instead.
+///
+/// The default implementation transforms properties that match @‎encode(BOOL)
+/// using the MTLBooleanValueTransformerName transformer.
+///
+/// objCType - The type encoding for the value of this property. This is the type
+///            as it would be returned by the @‎encode() directive.
+///
+/// Returns a value transformer or nil if no transformation should be used.
++ (NSValueTransformer *)transformerForModelPropertiesOfObjCType:(const char *)objCType;
 
 @end
 
+@interface MTLJSONAdapter (ValueTransformers)
+
+/// Creates a reversible transformer to convert a JSON dictionary into a MTLModel
+/// object, and vice-versa.
+///
+/// modelClass - The MTLModel subclass to attempt to parse from the JSON. This
+///              class must conform to <MTLJSONSerializing>. This argument must
+///              not be nil.
+///
+/// Returns a reversible transformer which uses the class of the receiver for
+/// transforming values back and forth.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)dictionaryTransformerWithModelClass:(Class)modelClass;
+
+/// Creates a reversible transformer to convert an array of JSON dictionaries
+/// into an array of MTLModel objects, and vice-versa.
+///
+/// modelClass - The MTLModel subclass to attempt to parse from each JSON
+///              dictionary. This class must conform to <MTLJSONSerializing>.
+///              This argument must not be nil.
+///
+/// Returns a reversible transformer which uses the class of the receiver for
+/// transforming array elements back and forth.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)arrayTransformerWithModelClass:(Class)modelClass;
+
+/// This value transformer is used by MTLJSONAdapter to automatically convert
+/// NSURL properties to JSON strings and vice versa.
++ (NSValueTransformer *)NSURLJSONTransformer;
+
+/// This value transformer is used by MTLJSONAdapter to automatically convert
+/// NSUUID properties to JSON strings and vice versa.
++ (NSValueTransformer *)NSUUIDJSONTransformer;
+
+@end
+
+@class MTLModel;
+
 @interface MTLJSONAdapter (Deprecated)
 
-+ (id)modelOfClass:(Class)modelClass fromJSONDictionary:(NSDictionary *)JSONDictionary __attribute__((deprecated("Replaced by +modelOfClass:fromJSONDictionary:error:")));
-- (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)modelClass __attribute__((deprecated("Replaced by -initWithJSONDictionary:modelClass:error:")));
+@property (nonatomic, strong, readonly) id<MTLJSONSerializing> model __attribute__((unavailable("Replaced by -modelFromJSONDictionary:error:")));
+
++ (NSArray *)JSONArrayFromModels:(NSArray *)models __attribute__((deprecated("Replaced by +JSONArrayFromModels:error:"))) NS_SWIFT_UNAVAILABLE("Replaced by +JSONArrayFromModels:error:");
+
++ (NSDictionary *)JSONDictionaryFromModel:(MTLModel<MTLJSONSerializing> *)model __attribute__((deprecated("Replaced by +JSONDictionaryFromModel:error:"))) NS_SWIFT_UNAVAILABLE("Replaced by +JSONDictionaryFromModel:error:");
+
+- (NSDictionary *)JSONDictionary __attribute__((unavailable("Replaced by -JSONDictionaryFromModel:error:"))) NS_SWIFT_UNAVAILABLE("Replaced by -JSONDictionaryFromModel:error:");
+- (NSString *)JSONKeyPathForPropertyKey:(NSString *)key __attribute__((unavailable("Replaced by -serializablePropertyKeys:forModel:")));
+- (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)modelClass error:(NSError **)error __attribute__((unavailable("Replaced by -initWithModelClass:")));
+- (id)initWithModel:(id<MTLJSONSerializing>)model __attribute__((unavailable("Replaced by -initWithModelClass:"))) NS_SWIFT_UNAVAILABLE("Replaced by -initWithModelClass:");
+- (NSDictionary *)serializeToJSONDictionary:(NSError **)error __attribute__((unavailable("Replaced by -JSONDictionaryFromModel:error:"))) NS_SWIFT_UNAVAILABLE("Replaced by -JSONDictionaryFromModel:error:");
 
 @end

Mantle/MTLJSONAdapter.m

@@ -6,9 +6,18 @@
 //  Copyright (c) 2013 GitHub. All rights reserved.
 //
 
+#import <objc/runtime.h>
+
+#import "NSDictionary+MTLJSONKeyPath.h"
+
+#import <Mantle/EXTRuntimeExtensions.h>
+#import <Mantle/EXTScope.h>
 #import "MTLJSONAdapter.h"
 #import "MTLModel.h"
+#import "MTLTransformerErrorHandling.h"
 #import "MTLReflection.h"
+#import "NSValueTransformer+MTLPredefinedTransformerAdditions.h"
+#import "MTLValueTransformer.h"
 
 NSString * const MTLJSONAdapterErrorDomain = @"MTLJSONAdapterErrorDomain";
 const NSInteger MTLJSONAdapterErrorNoClassFound = 2;
@@ -19,7 +28,7 @@ const NSInteger MTLJSONAdapterErrorInvalidJSONMapping = 4;
 const NSInteger MTLJSONAdapterErrorExceptionThrown = 1;
 
 // Associated with the NSException that was caught.
-static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapterThrownException";
+NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapterThrownException";
 
 @interface MTLJSONAdapter ()
 
@@ -30,12 +39,33 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 // A cached copy of the return value of +JSONKeyPathsByPropertyKey.
 @property (nonatomic, copy, readonly) NSDictionary *JSONKeyPathsByPropertyKey;
 
-// Looks up the NSValueTransformer that should be used for the given key.
+// A cached copy of the return value of -valueTransformersForModelClass:
+@property (nonatomic, copy, readonly) NSDictionary *valueTransformersByPropertyKey;
+
+// Used to cache the JSON adapters returned by -JSONAdapterForModelClass:error:.
+@property (nonatomic, strong, readonly) NSMapTable *JSONAdaptersByModelClass;
+
+// If +classForParsingJSONDictionary: returns a model class different from the
+// one this adapter was initialized with, use this method to obtain a cached
+// instance of a suitable adapter instead.
 //
-// key - The property key to transform from or to. This argument must not be nil.
+// modelClass - The class from which to parse the JSON. This class must conform
+//              to <MTLJSONSerializing>. This argument must not be nil.
+// error -      If not NULL, this may be set to an error that occurs during
+//              initializing the adapter.
 //
-// Returns a transformer to use, or nil to not transform the property.
-- (NSValueTransformer *)JSONTransformerForKey:(NSString *)key;
+// Returns a JSON adapter for modelClass, creating one of necessary. If no
+// adapter could be created, nil is returned.
+- (MTLJSONAdapter *)JSONAdapterForModelClass:(Class)modelClass error:(NSError **)error;
+
+// Collect all value transformers needed for a given class.
+//
+// modelClass - The class from which to parse the JSON. This class must conform
+//              to <MTLJSONSerializing>. This argument must not be nil.
+//
+// Returns a dictionary with the properties of modelClass that need
+// transformation as keys and the value transformers as values.
++ (NSDictionary *)valueTransformersForModelClass:(Class)modelClass;
 
 @end
 
@@ -44,8 +74,9 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 #pragma mark Convenience methods
 
 + (id)modelOfClass:(Class)modelClass fromJSONDictionary:(NSDictionary *)JSONDictionary error:(NSError **)error {
-	MTLJSONAdapter *adapter = [[self alloc] initWithJSONDictionary:JSONDictionary modelClass:modelClass error:error];
-	return adapter.model;
+	MTLJSONAdapter *adapter = [[self alloc] initWithModelClass:modelClass];
+
+	return [adapter modelFromJSONDictionary:JSONDictionary error:error];
 }
 
 + (NSArray *)modelsOfClass:(Class)modelClass fromJSONArray:(NSArray *)JSONArray error:(NSError **)error {
@@ -65,25 +96,26 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 		MTLModel *model = [self modelOfClass:modelClass fromJSONDictionary:JSONDictionary error:error];
 
 		if (model == nil) return nil;
-		
+
 		[models addObject:model];
 	}
-	
+
 	return models;
 }
 
-+ (NSDictionary *)JSONDictionaryFromModel:(MTLModel<MTLJSONSerializing> *)model {
-	MTLJSONAdapter *adapter = [[self alloc] initWithModel:model];
-	return adapter.JSONDictionary;
++ (NSDictionary *)JSONDictionaryFromModel:(id<MTLJSONSerializing>)model error:(NSError **)error {
+	MTLJSONAdapter *adapter = [[self alloc] initWithModelClass:model.class];
+
+	return [adapter JSONDictionaryFromModel:model error:error];
 }
 
-+ (NSArray *)JSONArrayFromModels:(NSArray *)models {
++ (NSArray *)JSONArrayFromModels:(NSArray *)models error:(NSError **)error {
 	NSParameterAssert(models != nil);
 	NSParameterAssert([models isKindOfClass:NSArray.class]);
 
 	NSMutableArray *JSONArray = [NSMutableArray arrayWithCapacity:models.count];
 	for (MTLModel<MTLJSONSerializing> *model in models) {
-		NSDictionary *JSONDictionary = [self JSONDictionaryFromModel:model];
+		NSDictionary *JSONDictionary = [self JSONDictionaryFromModel:model error:error];
 		if (JSONDictionary == nil) return nil;
 
 		[JSONArray addObject:JSONDictionary];
@@ -95,29 +127,139 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 #pragma mark Lifecycle
 
 - (id)init {
-	NSAssert(NO, @"%@ must be initialized with a JSON dictionary or model object", self.class);
+	NSAssert(NO, @"%@ must be initialized with a model class", self.class);
 	return nil;
 }
 
-- (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)modelClass error:(NSError **)error {
+- (id)initWithModelClass:(Class)modelClass {
 	NSParameterAssert(modelClass != nil);
-	NSParameterAssert([modelClass isSubclassOfClass:MTLModel.class]);
 	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)]);
 
-	if (JSONDictionary == nil || ![JSONDictionary isKindOfClass:NSDictionary.class]) {
-		if (error != NULL) {
-			NSDictionary *userInfo = @{
-				NSLocalizedDescriptionKey: NSLocalizedString(@"Missing JSON dictionary", @""),
-				NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"%@ could not be created because an invalid JSON dictionary was provided: %@", @""), NSStringFromClass(modelClass), JSONDictionary.class],
-			};
-			*error = [NSError errorWithDomain:MTLJSONAdapterErrorDomain code:MTLJSONAdapterErrorInvalidJSONDictionary userInfo:userInfo];
+	self = [super init];
+	if (self == nil) return nil;
+
+	_modelClass = modelClass;
+
+	_JSONKeyPathsByPropertyKey = [modelClass JSONKeyPathsByPropertyKey];
+
+	NSSet *propertyKeys = [self.modelClass propertyKeys];
+
+	for (NSString *mappedPropertyKey in _JSONKeyPathsByPropertyKey) {
+		if (![propertyKeys containsObject:mappedPropertyKey]) {
+			NSAssert(NO, @"%@ is not a property of %@.", mappedPropertyKey, modelClass);
+			return nil;
+		}
+
+		id value = _JSONKeyPathsByPropertyKey[mappedPropertyKey];
+
+		if ([value isKindOfClass:NSArray.class]) {
+			for (NSString *keyPath in value) {
+				if ([keyPath isKindOfClass:NSString.class]) continue;
+
+				NSAssert(NO, @"%@ must either map to a JSON key path or a JSON array of key paths, got: %@.", mappedPropertyKey, value);
+				return nil;
+			}
+		} else if (![value isKindOfClass:NSString.class]) {
+			NSAssert(NO, @"%@ must either map to a JSON key path or a JSON array of key paths, got: %@.",mappedPropertyKey, value);
+			return nil;
 		}
-		return nil;
 	}
 
-	if ([modelClass respondsToSelector:@selector(classForParsingJSONDictionary:)]) {
-		modelClass = [modelClass classForParsingJSONDictionary:JSONDictionary];
-		if (modelClass == nil) {
+	_valueTransformersByPropertyKey = [self.class valueTransformersForModelClass:modelClass];
+
+	_JSONAdaptersByModelClass = [NSMapTable strongToStrongObjectsMapTable];
+
+	return self;
+}
+
+#pragma mark Serialization
+
+- (NSDictionary *)JSONDictionaryFromModel:(id<MTLJSONSerializing>)model error:(NSError **)error {
+	NSParameterAssert(model != nil);
+	NSParameterAssert([model isKindOfClass:self.modelClass]);
+
+	if (self.modelClass != model.class) {
+		MTLJSONAdapter *otherAdapter = [self JSONAdapterForModelClass:model.class error:error];
+
+		return [otherAdapter JSONDictionaryFromModel:model error:error];
+	}
+
+	NSSet *propertyKeysToSerialize = [self serializablePropertyKeys:[NSSet setWithArray:self.JSONKeyPathsByPropertyKey.allKeys] forModel:model];
+
+	NSDictionary *dictionaryValue = [model.dictionaryValue dictionaryWithValuesForKeys:propertyKeysToSerialize.allObjects];
+	NSMutableDictionary *JSONDictionary = [[NSMutableDictionary alloc] initWithCapacity:dictionaryValue.count];
+
+	__block BOOL success = YES;
+	__block NSError *tmpError = nil;
+
+	[dictionaryValue enumerateKeysAndObjectsUsingBlock:^(NSString *propertyKey, id value, BOOL *stop) {
+		id JSONKeyPaths = self.JSONKeyPathsByPropertyKey[propertyKey];
+
+		if (JSONKeyPaths == nil) return;
+
+		NSValueTransformer *transformer = self.valueTransformersByPropertyKey[propertyKey];
+		if ([transformer.class allowsReverseTransformation]) {
+			// Map NSNull -> nil for the transformer, and then back for the
+			// dictionaryValue we're going to insert into.
+			if ([value isEqual:NSNull.null]) value = nil;
+
+			if ([transformer respondsToSelector:@selector(reverseTransformedValue:success:error:)]) {
+				id<MTLTransformerErrorHandling> errorHandlingTransformer = (id)transformer;
+
+				value = [errorHandlingTransformer reverseTransformedValue:value success:&success error:&tmpError];
+
+				if (!success) {
+					*stop = YES;
+					return;
+				}
+			} else {
+				value = [transformer reverseTransformedValue:value] ?: NSNull.null;
+			}
+		}
+
+		void (^createComponents)(id, NSString *) = ^(id obj, NSString *keyPath) {
+			NSArray *keyPathComponents = [keyPath componentsSeparatedByString:@"."];
+
+			// Set up dictionaries at each step of the key path.
+			for (NSString *component in keyPathComponents) {
+				if ([obj valueForKey:component] == nil) {
+					// Insert an empty mutable dictionary at this spot so that we
+					// can set the whole key path afterward.
+					[obj setValue:[NSMutableDictionary dictionary] forKey:component];
+				}
+
+				obj = [obj valueForKey:component];
+			}
+		};
+
+		if ([JSONKeyPaths isKindOfClass:NSString.class]) {
+			createComponents(JSONDictionary, JSONKeyPaths);
+
+			[JSONDictionary setValue:value forKeyPath:JSONKeyPaths];
+		}
+
+		if ([JSONKeyPaths isKindOfClass:NSArray.class]) {
+			for (NSString *JSONKeyPath in JSONKeyPaths) {
+				createComponents(JSONDictionary, JSONKeyPath);
+
+				[JSONDictionary setValue:value[JSONKeyPath] forKeyPath:JSONKeyPath];
+			}
+		}
+	}];
+
+	if (success) {
+		return JSONDictionary;
+	} else {
+		if (error != NULL) *error = tmpError;
+
+		return nil;
+	}
+}
+
+- (id)modelFromJSONDictionary:(NSDictionary *)JSONDictionary error:(NSError **)error {
+	if ([self.modelClass respondsToSelector:@selector(classForParsingJSONDictionary:)]) {
+		Class class = [self.modelClass classForParsingJSONDictionary:JSONDictionary];
+		if (class == nil) {
 			if (error != NULL) {
 				NSDictionary *userInfo = @{
 					NSLocalizedDescriptionKey: NSLocalizedString(@"Could not parse JSON", @""),
@@ -130,69 +272,70 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 			return nil;
 		}
 
-		NSAssert([modelClass isSubclassOfClass:MTLModel.class], @"Class %@ returned from +classForParsingJSONDictionary: is not a subclass of MTLModel", modelClass);
-		NSAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)], @"Class %@ returned from +classForParsingJSONDictionary: does not conform to <MTLJSONSerializing>", modelClass);
+		if (class != self.modelClass) {
+			NSAssert([class conformsToProtocol:@protocol(MTLJSONSerializing)], @"Class %@ returned from +classForParsingJSONDictionary: does not conform to <MTLJSONSerializing>", class);
+
+			MTLJSONAdapter *otherAdapter = [self JSONAdapterForModelClass:class error:error];
+
+			return [otherAdapter modelFromJSONDictionary:JSONDictionary error:error];
+		}
 	}
 
-	self = [super init];
-	if (self == nil) return nil;
-
-	_modelClass = modelClass;
-	_JSONKeyPathsByPropertyKey = [[modelClass JSONKeyPathsByPropertyKey] copy];
-
 	NSMutableDictionary *dictionaryValue = [[NSMutableDictionary alloc] initWithCapacity:JSONDictionary.count];
 
-	NSSet *propertyKeys = [self.modelClass propertyKeys];
+	for (NSString *propertyKey in [self.modelClass propertyKeys]) {
+		id JSONKeyPaths = self.JSONKeyPathsByPropertyKey[propertyKey];
 
-	for (NSString *mappedPropertyKey in self.JSONKeyPathsByPropertyKey) {
-		if (![propertyKeys containsObject:mappedPropertyKey]) {
-			NSAssert(NO, @"%@ is not a property of %@.", mappedPropertyKey, modelClass);
-			return nil;
-		}
-
-		id value = self.JSONKeyPathsByPropertyKey[mappedPropertyKey];
-
-		if (![value isKindOfClass:NSString.class] && value != NSNull.null) {
-			NSAssert(NO, @"%@ must either map to a JSON key path or NSNull, got: %@.",mappedPropertyKey, value);
-			return nil;
-		}
-	}
-
-	for (NSString *propertyKey in propertyKeys) {
-		NSString *JSONKeyPath = [self JSONKeyPathForPropertyKey:propertyKey];
-		if (JSONKeyPath == nil) continue;
+		if (JSONKeyPaths == nil) continue;
 
 		id value;
-		@try {
-			value = [JSONDictionary valueForKeyPath:JSONKeyPath];
-		} @catch (NSException *ex) {
-			if (error != NULL) {
-				NSDictionary *userInfo = @{
-					NSLocalizedDescriptionKey: NSLocalizedString(@"Invalid JSON dictionary", nil),
-					NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"%1$@ could not be parsed because an invalid JSON dictionary was provided for key path \"%2$@\"", nil), modelClass, JSONKeyPath],
-					MTLJSONAdapterThrownExceptionErrorKey: ex
-				};
 
-				*error = [NSError errorWithDomain:MTLJSONAdapterErrorDomain code:MTLJSONAdapterErrorInvalidJSONDictionary userInfo:userInfo];
+		if ([JSONKeyPaths isKindOfClass:NSArray.class]) {
+			NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
+
+			for (NSString *keyPath in JSONKeyPaths) {
+				BOOL success = NO;
+				id value = [JSONDictionary mtl_valueForJSONKeyPath:keyPath success:&success error:error];
+
+				if (!success) return nil;
+
+				if (value != nil) dictionary[keyPath] = value;
 			}
 
-			return nil;
+			value = dictionary;
+		} else {
+			BOOL success = NO;
+			value = [JSONDictionary mtl_valueForJSONKeyPath:JSONKeyPaths success:&success error:error];
+
+			if (!success) return nil;
 		}
 
 		if (value == nil) continue;
 
 		@try {
-			NSValueTransformer *transformer = [self JSONTransformerForKey:propertyKey];
+			NSValueTransformer *transformer = self.valueTransformersByPropertyKey[propertyKey];
 			if (transformer != nil) {
 				// Map NSNull -> nil for the transformer, and then back for the
 				// dictionary we're going to insert into.
 				if ([value isEqual:NSNull.null]) value = nil;
-				value = [transformer transformedValue:value] ?: NSNull.null;
+
+				if ([transformer respondsToSelector:@selector(transformedValue:success:error:)]) {
+					id<MTLTransformerErrorHandling> errorHandlingTransformer = (id)transformer;
+
+					BOOL success = YES;
+					value = [errorHandlingTransformer transformedValue:value success:&success error:error];
+
+					if (!success) return nil;
+				} else {
+					value = [transformer transformedValue:value];
+				}
+
+				if (value == nil) value = NSNull.null;
 			}
 
 			dictionaryValue[propertyKey] = value;
 		} @catch (NSException *ex) {
-			NSLog(@"*** Caught exception %@ parsing JSON key path \"%@\" from: %@", ex, JSONKeyPath, JSONDictionary);
+			NSLog(@"*** Caught exception %@ parsing JSON key path \"%@\" from: %@", ex, JSONKeyPaths, JSONDictionary);
 
 			// Fail fast in Debug builds.
 			#if DEBUG
@@ -200,7 +343,8 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 			#else
 			if (error != NULL) {
 				NSDictionary *userInfo = @{
-					NSLocalizedDescriptionKey: ex.description,
+					NSLocalizedDescriptionKey: [NSString stringWithFormat:@"Caught exception parsing JSON key path \"%@\" for model class: %@", JSONKeyPaths, self.modelClass],
+					NSLocalizedRecoverySuggestionErrorKey: ex.description,
 					NSLocalizedFailureReasonErrorKey: ex.reason,
 					MTLJSONAdapterThrownExceptionErrorKey: ex
 				};
@@ -213,92 +357,295 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 		}
 	}
 
-	_model = [self.modelClass modelWithDictionary:dictionaryValue error:error];
-	if (_model == nil) return nil;
+	id model = [self.modelClass modelWithDictionary:dictionaryValue error:error];
 
-	return self;
+	return [model validate:error] ? model : nil;
 }
 
-- (id)initWithModel:(MTLModel<MTLJSONSerializing> *)model {
-	NSParameterAssert(model != nil);
++ (NSDictionary *)valueTransformersForModelClass:(Class)modelClass {
+	NSParameterAssert(modelClass != nil);
+	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)]);
 
-	self = [super init];
-	if (self == nil) return nil;
+	NSMutableDictionary *result = [NSMutableDictionary dictionary];
 
-	_model = model;
-	_modelClass = model.class;
-	_JSONKeyPathsByPropertyKey = [[model.class JSONKeyPathsByPropertyKey] copy];
+	for (NSString *key in [modelClass propertyKeys]) {
+		SEL selector = MTLSelectorWithKeyPattern(key, "JSONTransformer");
+		if ([modelClass respondsToSelector:selector]) {
+			IMP imp = [modelClass methodForSelector:selector];
+			NSValueTransformer * (*function)(id, SEL) = (__typeof__(function))imp;
+			NSValueTransformer *transformer = function(modelClass, selector);
 
-	return self;
-}
+			if (transformer != nil) result[key] = transformer;
 
-#pragma mark Serialization
-
-- (NSDictionary *)JSONDictionary {
-	NSDictionary *dictionaryValue = self.model.dictionaryValue;
-	NSMutableDictionary *JSONDictionary = [[NSMutableDictionary alloc] initWithCapacity:dictionaryValue.count];
-
-	[dictionaryValue enumerateKeysAndObjectsUsingBlock:^(NSString *propertyKey, id value, BOOL *stop) {
-		NSString *JSONKeyPath = [self JSONKeyPathForPropertyKey:propertyKey];
-		if (JSONKeyPath == nil) return;
-
-		NSValueTransformer *transformer = [self JSONTransformerForKey:propertyKey];
-		if ([transformer.class allowsReverseTransformation]) {
-			// Map NSNull -> nil for the transformer, and then back for the
-			// dictionaryValue we're going to insert into.
-			if ([value isEqual:NSNull.null]) value = nil;
-			value = [transformer reverseTransformedValue:value] ?: NSNull.null;
+			continue;
 		}
 
-		NSArray *keyPathComponents = [JSONKeyPath componentsSeparatedByString:@"."];
+		if ([modelClass respondsToSelector:@selector(JSONTransformerForKey:)]) {
+			NSValueTransformer *transformer = [modelClass JSONTransformerForKey:key];
 
-		// Set up dictionaries at each step of the key path.
-		id obj = JSONDictionary;
-		for (NSString *component in keyPathComponents) {
-			if ([obj valueForKey:component] == nil) {
-				// Insert an empty mutable dictionary at this spot so that we
-				// can set the whole key path afterward.
-				[obj setValue:[NSMutableDictionary dictionary] forKey:component];
+			if (transformer != nil) {
+				result[key] = transformer;
+				continue;
+			}
+		}
+
+		objc_property_t property = class_getProperty(modelClass, key.UTF8String);
+
+		if (property == NULL) continue;
+
+		mtl_propertyAttributes *attributes = mtl_copyPropertyAttributes(property);
+		@onExit {
+			free(attributes);
+		};
+
+		NSValueTransformer *transformer = nil;
+
+		if (*(attributes->type) == *(@encode(id))) {
+			Class propertyClass = attributes->objectClass;
+
+			if (propertyClass != nil) {
+				transformer = [self transformerForModelPropertiesOfClass:propertyClass];
 			}
 
-			obj = [obj valueForKey:component];
+
+			// For user-defined MTLModel, try parse it with dictionaryTransformer.
+			if (nil == transformer && [propertyClass conformsToProtocol:@protocol(MTLJSONSerializing)]) {
+				transformer = [self dictionaryTransformerWithModelClass:propertyClass];
+			}
+			
+			if (transformer == nil) transformer = [NSValueTransformer mtl_validatingTransformerForClass:propertyClass ?: NSObject.class];
+		} else {
+			transformer = [self transformerForModelPropertiesOfObjCType:attributes->type] ?: [NSValueTransformer mtl_validatingTransformerForClass:NSValue.class];
 		}
 
-		[JSONDictionary setValue:value forKeyPath:JSONKeyPath];
-	}];
-
-	return JSONDictionary;
-}
-
-- (NSValueTransformer *)JSONTransformerForKey:(NSString *)key {
-	NSParameterAssert(key != nil);
-
-	SEL selector = MTLSelectorWithKeyPattern(key, "JSONTransformer");
-	if ([self.modelClass respondsToSelector:selector]) {
-		IMP imp = [self.modelClass methodForSelector:selector];
-		NSValueTransformer * (*function)(id, SEL) = (__typeof__(function))imp;
-		NSValueTransformer *transformer = function(self.modelClass, selector);
-		return transformer;
+		if (transformer != nil) result[key] = transformer;
 	}
 
-	if ([self.modelClass respondsToSelector:@selector(JSONTransformerForKey:)]) {
-		return [self.modelClass JSONTransformerForKey:key];
+	return result;
+}
+
+- (MTLJSONAdapter *)JSONAdapterForModelClass:(Class)modelClass error:(NSError **)error {
+	NSParameterAssert(modelClass != nil);
+	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)]);
+
+	@synchronized(self) {
+		MTLJSONAdapter *result = [self.JSONAdaptersByModelClass objectForKey:modelClass];
+
+		if (result != nil) return result;
+
+		result = [[self.class alloc] initWithModelClass:modelClass];
+
+		if (result != nil) {
+			[self.JSONAdaptersByModelClass setObject:result forKey:modelClass];
+		}
+
+		return result;
+	}
+}
+
+- (NSSet *)serializablePropertyKeys:(NSSet *)propertyKeys forModel:(id<MTLJSONSerializing>)model {
+	return propertyKeys;
+}
+
++ (NSValueTransformer *)transformerForModelPropertiesOfClass:(Class)modelClass {
+	NSParameterAssert(modelClass != nil);
+
+	SEL selector = MTLSelectorWithKeyPattern(NSStringFromClass(modelClass), "JSONTransformer");
+	if (![self respondsToSelector:selector]) return nil;
+	
+	IMP imp = [self methodForSelector:selector];
+	NSValueTransformer * (*function)(id, SEL) = (__typeof__(function))imp;
+	NSValueTransformer *result = function(self, selector);
+	
+	return result;
+}
+
++ (NSValueTransformer *)transformerForModelPropertiesOfObjCType:(const char *)objCType {
+	NSParameterAssert(objCType != NULL);
+
+	if (strcmp(objCType, @encode(BOOL)) == 0) {
+		return [NSValueTransformer valueTransformerForName:MTLBooleanValueTransformerName];
 	}
 
 	return nil;
 }
 
-- (NSString *)JSONKeyPathForPropertyKey:(NSString *)key {
-	NSParameterAssert(key != nil);
+@end
 
-	id JSONKeyPath = self.JSONKeyPathsByPropertyKey[key];
-	if ([JSONKeyPath isEqual:NSNull.null]) return nil;
+@implementation MTLJSONAdapter (ValueTransformers)
 
-	if (JSONKeyPath == nil) {
-		return key;
-	} else {
-		return JSONKeyPath;
-	}
++ (NSValueTransformer<MTLTransformerErrorHandling> *)dictionaryTransformerWithModelClass:(Class)modelClass {
+	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLModel)]);
+	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)]);
+	__block MTLJSONAdapter *adapter;
+	
+	return [MTLValueTransformer
+		transformerUsingForwardBlock:^ id (id JSONDictionary, BOOL *success, NSError **error) {
+			if (JSONDictionary == nil) return nil;
+			
+			if (![JSONDictionary isKindOfClass:NSDictionary.class]) {
+				if (error != NULL) {
+					NSDictionary *userInfo = @{
+						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert JSON dictionary to model object", @""),
+						NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSDictionary, got: %@", @""), JSONDictionary],
+						MTLTransformerErrorHandlingInputValueErrorKey : JSONDictionary
+					};
+					
+					*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+				}
+				*success = NO;
+				return nil;
+			}
+
+			if (!adapter) {
+				adapter = [[self alloc] initWithModelClass:modelClass];
+			}
+			id model = [adapter modelFromJSONDictionary:JSONDictionary error:error];
+			if (model == nil) {
+				*success = NO;
+			}
+
+			return model;
+		}
+		reverseBlock:^ NSDictionary * (id model, BOOL *success, NSError **error) {
+			if (model == nil) return nil;
+			
+			if (![model conformsToProtocol:@protocol(MTLModel)] || ![model conformsToProtocol:@protocol(MTLJSONSerializing)]) {
+				if (error != NULL) {
+					NSDictionary *userInfo = @{
+						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert model object to JSON dictionary", @""),
+						NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected a MTLModel object conforming to <MTLJSONSerializing>, got: %@.", @""), model],
+						MTLTransformerErrorHandlingInputValueErrorKey : model
+					};
+					
+					*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+				}
+				*success = NO;
+				return nil;
+			}
+
+			if (!adapter) {
+				adapter = [[self alloc] initWithModelClass:modelClass];
+			}
+			NSDictionary *result = [adapter JSONDictionaryFromModel:model error:error];
+			if (result == nil) {
+				*success = NO;
+			}
+
+			return result;
+		}];
+}
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)arrayTransformerWithModelClass:(Class)modelClass {
+	id<MTLTransformerErrorHandling> dictionaryTransformer = [self dictionaryTransformerWithModelClass:modelClass];
+	
+	return [MTLValueTransformer
+		transformerUsingForwardBlock:^ id (NSArray *dictionaries, BOOL *success, NSError **error) {
+			if (dictionaries == nil) return nil;
+			
+			if (![dictionaries isKindOfClass:NSArray.class]) {
+				if (error != NULL) {
+					NSDictionary *userInfo = @{
+						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert JSON array to model array", @""),
+						NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSArray, got: %@.", @""), dictionaries],
+						MTLTransformerErrorHandlingInputValueErrorKey : dictionaries
+					};
+					
+					*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+				}
+				*success = NO;
+				return nil;
+			}
+			
+			NSMutableArray *models = [NSMutableArray arrayWithCapacity:dictionaries.count];
+			for (id JSONDictionary in dictionaries) {
+				if (JSONDictionary == NSNull.null) {
+					[models addObject:NSNull.null];
+					continue;
+				}
+				
+				if (![JSONDictionary isKindOfClass:NSDictionary.class]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert JSON array to model array", @""),
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSDictionary or an NSNull, got: %@.", @""), JSONDictionary],
+							MTLTransformerErrorHandlingInputValueErrorKey : JSONDictionary
+						};
+						
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+				
+				id model = [dictionaryTransformer transformedValue:JSONDictionary success:success error:error];
+				
+				if (*success == NO) return nil;
+				
+				if (model == nil) continue;
+				
+				[models addObject:model];
+			}
+			
+			return models;
+		}
+		reverseBlock:^ id (NSArray *models, BOOL *success, NSError **error) {
+			if (models == nil) return nil;
+			
+			if (![models isKindOfClass:NSArray.class]) {
+				if (error != NULL) {
+					NSDictionary *userInfo = @{
+						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert model array to JSON array", @""),
+						NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSArray, got: %@.", @""), models],
+						MTLTransformerErrorHandlingInputValueErrorKey : models
+					};
+					
+					*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+				}
+				*success = NO;
+				return nil;
+			}
+			
+			NSMutableArray *dictionaries = [NSMutableArray arrayWithCapacity:models.count];
+			for (id model in models) {
+				if (model == NSNull.null) {
+					[dictionaries addObject:NSNull.null];
+					continue;
+				}
+				
+				if (![model isKindOfClass:MTLModel.class]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert JSON array to model array", @""),
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected a MTLModel or an NSNull, got: %@.", @""), model],
+							MTLTransformerErrorHandlingInputValueErrorKey : model
+						};
+						
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+				
+				NSDictionary *dict = [dictionaryTransformer reverseTransformedValue:model success:success error:error];
+				
+				if (*success == NO) return nil;
+				
+				if (dict == nil) continue;
+				
+				[dictionaries addObject:dict];
+			}
+			
+			return dictionaries;
+		}];
+}
+
++ (NSValueTransformer *)NSURLJSONTransformer {
+	return [NSValueTransformer valueTransformerForName:MTLURLValueTransformerName];
+}
+
++ (NSValueTransformer *)NSUUIDJSONTransformer {
+	return [NSValueTransformer valueTransformerForName:MTLUUIDValueTransformerName];
 }
 
 @end
@@ -308,12 +655,12 @@ static NSString * const MTLJSONAdapterThrownExceptionErrorKey = @"MTLJSONAdapter
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated-implementations"
 
-+ (id)modelOfClass:(Class)modelClass fromJSONDictionary:(NSDictionary *)JSONDictionary {
-	return [self modelOfClass:modelClass fromJSONDictionary:JSONDictionary error:NULL];
++ (NSArray *)JSONArrayFromModels:(NSArray *)models {
+	return [self JSONArrayFromModels:models error:NULL];
 }
 
-- (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)modelClass {
-	return [self initWithJSONDictionary:JSONDictionary modelClass:modelClass error:NULL];
++ (NSDictionary *)JSONDictionaryFromModel:(MTLModel<MTLJSONSerializing> *)model {
+	return [self JSONDictionaryFromModel:model error:NULL];
 }
 
 #pragma clang diagnostic pop

Mantle/MTLManagedObjectAdapter.h

@@ -1,215 +0,0 @@
-//
-//  MTLManagedObjectAdapter.h
-//  Mantle
-//
-//  Created by Justin Spahr-Summers on 2013-03-29.
-//  Copyright (c) 2013 GitHub. All rights reserved.
-//
-
-#import <CoreData/CoreData.h>
-
-@class MTLModel;
-
-// A MTLModel object that supports being serialized to and from Core Data as an
-// NSManagedObject.
-@protocol MTLManagedObjectSerializing
-@required
-
-// The name of the Core Data entity that the receiver serializes to and
-// deserializes from.
-//
-// This method must not return nil.
-+ (NSString *)managedObjectEntityName;
-
-// Specifies how to map property keys to different keys on the receiver's
-// +managedObjectEntity.
-//
-// Entity attributes will be mapped to and from the receiver's properties using
-// +entityAttributeTransformerForKey:. Entity relationships will be mapped to
-// and from MTLModel objects using +relationshipModelClassesByPropertyKey.
-// Fetched properties are not supported.
-//
-// Subclasses overriding this method should combine their values with those of
-// `super`.
-//
-// Any property keys not present in the dictionary are assumed to match the
-// entity key that should be used. Any keys associated with NSNull will not
-// participate in managed object serialization.
-//
-// Returns a dictionary mapping property keys to entity keys (as strings) or
-// NSNull values.
-+ (NSDictionary *)managedObjectKeysByPropertyKey;
-
-@optional
-
-// Specifies a set of property keys used by the adapter to check for an already
-// existing managed object when converting the MTLModel to its related
-// NSManagedObject.
-//
-// The adapter will first map any keys provided by this method to the correct
-// keys in managedObjectKeysByPropertyKey.
-//
-// The adapter will then perform a fetch request in the provided context for a
-// managed object that matches the MTLModel's managedObjectEntityName and has
-// equal values set for the property keys on the MTLModel.
-//
-// The managed object returned by the fetch request will then be set with all
-// values from the MTLModel that the managed object is being converted from.
-//
-// If a property value of our MTLModel is yet another MTLModel which needs to be
-// converted to a managed object, the class for that MTLModel can also implement
-// this method to perform its own uniqing.
-//
-// For example:
-// 1. An MTLModel subclass has id_number = 10.
-// 2. An NSManagedObject accessible to the adapter's context has idnumber = 10.
-// 3. managedObjectKeysByPropertyKey returns @{@"id_number" : @"idnumber"}
-// 4. propertyKeysForManagedObjectUniquing returns
-//    [NSSet setWithObject:@"id_number"];
-// 5. Then our fetch request may return this managed object (or another managed
-//    object with idnumber = 10).
-//
-// NOTE: If multiple managed objects follow the same uniquing criteria only one
-// of them will be set with our MTLModel's values.
-+ (NSSet *)propertyKeysForManagedObjectUniquing;
-
-// Specifies how to convert the given property key to a managed object
-// attribute. If reversible, the transformer will also be used to convert the
-// managed object attribute back to the property.
-//
-// If the receiver implements a `+<key>EntityAttributeTransformer` method,
-// MTLManagedObjectAdapter will use the result of that method instead.
-//
-// Returns a value transformer, or nil if no transformation should be performed.
-+ (NSValueTransformer *)entityAttributeTransformerForKey:(NSString *)key;
-
-// Specifies the MTLModel subclasses that should be deserialized to the
-// receiver's property keys when a property key corresponds to an entity
-// relationship.
-//
-// In other words, the dictionary returned by this method is used to decode
-// managed object relationships into MTLModels (or NSArrays or NSSets thereof)
-// set on the receiver.
-//
-// If a property key is omitted from the returned dictionary, but present in
-// +managedObjectKeysByPropertyKey, and the receiver's +managedObjectEntity has
-// a relationship at the corresponding key, an exception will be thrown during
-// deserialization.
-//
-// Subclasses overriding this method should combine their values with those of
-// `super`.
-//
-// Returns a dictionary mapping property keys to the Class objects that should
-// be used.
-+ (NSDictionary *)relationshipModelClassesByPropertyKey;
-
-// Overridden to deserialize a different class instead of the receiver, based on
-// information in the provided object.
-//
-// This is mostly useful for class clusters, where the abstract base class would
-// be passed into +[MTLManagedObjectAdapter
-// modelOfClass:fromManagedObject:error:], but a subclass should be instantiated
-// instead.
-//
-// managedObject - The object that will be deserialized.
-//
-// Returns the class that should be instantiated (which may be the receiver), or
-// nil to abort parsing (e.g., if the data is invalid).
-+ (Class)classForDeserializingManagedObject:(NSManagedObject *)managedObject;
-
-// Overriden when merging the value of the given key on the receiver with the
-// value of the same key from the given `NSManagedObject` requires custom
-// handling.
-//
-// By default, this method is not implemented, and precedence will be given to
-// the value of the receiving model implicitly.
-//
-// When implemented, this method is called when an existing `NSManagedObject`
-// is found for the receiving model, before updating the `NSManagedObject`'s
-// properties.
-//
-// When implementing, you should use `+managedObjectKeysByPropertyKey` to map
-// the given `key` to the appropriate `NSManagedObject` property.
-- (void)mergeValueForKey:(NSString *)key fromManagedObject:(NSManagedObject *)managedObject;
-
-// Overriden when merging values on the receiver with the given
-// `NSManagedObject` requires custom handling.
-//
-// By default, this method is not implemented, and precedence will be given to
-// the values of the receiving model implicitly.
-//
-// When implemented, this method is called when an existing `NSManagedObject`
-// is found for the receiving model, before updating the `NSManagedObject`'s
-// properties.
-//
-// When implementing, you should use `+managedObjectKeysByPropertyKey` to map
-// the given `key` to the appropriate `NSManagedObject` property.
-//
-// If you have also implemented `mergeValueForKey:fromManagedObject:` you have
-// to make sure to call `mergeValueForKey:fromManagedObject:` from this method
-// when appropriate.
-- (void)mergeValuesForKeysFromManagedObject:(NSManagedObject *)managedObject;
-
-@end
-
-// The domain for errors originating from MTLManagedObjectAdapter.
-extern NSString * const MTLManagedObjectAdapterErrorDomain;
-
-// +classForDeserializingManagedObject: returned nil for the given object.
-extern const NSInteger MTLManagedObjectAdapterErrorNoClassFound;
-
-// An NSManagedObject failed to initialize.
-extern const NSInteger MTLManagedObjectAdapterErrorInitializationFailed;
-
-// The managed object key specified by +managedObjectKeysByPropertyKey does not
-// exist in the NSEntityDescription.
-extern const NSInteger MTLManagedObjectAdapterErrorInvalidManagedObjectKey;
-
-// The managed object property specified has a type that isn't supported by
-// MTLManagedObjectAdapter.
-extern const NSInteger MTLManagedObjectAdapterErrorUnsupportedManagedObjectPropertyType;
-
-// The fetch request to find an existing managed object based on
-// `+propertyKeysForManagedObjectUniquing` failed.
-extern const NSInteger MTLManagedObjectAdapterErrorUniqueFetchRequestFailed;
-
-// A MTLModel property cannot be serialized to or deserialized from an
-// NSManagedObject relationship.
-//
-// For a to-one relationship, this means that the property does not contain
-// a MTLModel, or the MTLModel does not conform to <MTLManagedObjectSerializing>.
-//
-// For a to-many relationship, this means that the property does not contain an
-// NSArray or NSSet of MTLModel<MTLManagedObjectSerializing> instances.
-extern const NSInteger MTLManagedObjectAdapterErrorUnsupportedRelationshipClass;
-
-// The model's implementation of +managedObjectKeysByPropertyKey included a key
-// which does not actually exist in +propertyKeys.
-extern const NSInteger MTLManagedObjectAdapterErrorInvalidManagedObjectMapping;
-
-// Converts a MTLModel object to and from an NSManagedObject.
-@interface MTLManagedObjectAdapter : NSObject
-
-// Attempts to deserialize an NSManagedObject into a MTLModel object.
-//
-// modelClass    - The MTLModel subclass to return. This class must conform to
-//                 <MTLManagedObjectSerializing>. This argument must not be nil.
-// managedObject - The managed object to deserialize. If this argument is nil,
-//                 the method returns nil.
-// error         - If not NULL, this may be set to an error that occurs during
-//                 deserialization or initializing an instance of `modelClass`.
-//
-// Returns an instance of `modelClass` upon success, or nil if an error
-// occurred.
-+ (id)modelOfClass:(Class)modelClass fromManagedObject:(NSManagedObject *)managedObject error:(NSError **)error;
-
-// Serializes a MTLModel into an NSManagedObject.
-//
-// model   - The model object to serialize. This argument must not be nil.
-// context - The context into which to insert the created managed object. This
-//           argument must not be nil.
-// error   - If not NULL, this may be set to an error that occurs during
-//           serialization or insertion.
-+ (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context error:(NSError **)error;
-
-@end

Mantle/MTLManagedObjectAdapter.m

@@ -1,641 +0,0 @@
-//
-//  MTLManagedObjectAdapter.m
-//  Mantle
-//
-//  Created by Justin Spahr-Summers on 2013-03-29.
-//  Copyright (c) 2013 GitHub. All rights reserved.
-//
-
-#import "MTLManagedObjectAdapter.h"
-#import "MTLEXTScope.h"
-#import "MTLModel.h"
-#import "MTLReflection.h"
-#import "NSArray+MTLManipulationAdditions.h"
-
-NSString * const MTLManagedObjectAdapterErrorDomain = @"MTLManagedObjectAdapterErrorDomain";
-const NSInteger MTLManagedObjectAdapterErrorNoClassFound = 2;
-const NSInteger MTLManagedObjectAdapterErrorInitializationFailed = 3;
-const NSInteger MTLManagedObjectAdapterErrorInvalidManagedObjectKey = 4;
-const NSInteger MTLManagedObjectAdapterErrorUnsupportedManagedObjectPropertyType = 5;
-const NSInteger MTLManagedObjectAdapterErrorUnsupportedRelationshipClass = 6;
-const NSInteger MTLManagedObjectAdapterErrorUniqueFetchRequestFailed = 7;
-const NSInteger MTLManagedObjectAdapterErrorInvalidManagedObjectMapping = 8;
-
-// Performs the given block in the context's queue, if it has one.
-static id performInContext(NSManagedObjectContext *context, id (^block)(void)) {
-	if (context.concurrencyType == NSConfinementConcurrencyType) {
-		return block();
-	}
-
-	__block id result = nil;
-	[context performBlockAndWait:^{
-		result = block();
-	}];
-
-	return result;
-}
-
-@interface MTLManagedObjectAdapter ()
-
-// The MTLModel subclass being serialized or deserialized.
-@property (nonatomic, strong, readonly) Class modelClass;
-
-// A cached copy of the return value of +managedObjectKeysByPropertyKey.
-@property (nonatomic, copy, readonly) NSDictionary *managedObjectKeysByPropertyKey;
-
-// A cached copy of the return value of +relationshipModelClassesByPropertyKey.
-@property (nonatomic, copy, readonly) NSDictionary *relationshipModelClassesByPropertyKey;
-
-// Initializes the receiver to serialize or deserialize a MTLModel of the given
-// class.
-- (id)initWithModelClass:(Class)modelClass;
-
-// Invoked from +modelOfClass:fromManagedObject:processedObjects:error: after
-// the receiver's properties have been initialized.
-- (id)modelFromManagedObject:(NSManagedObject *)managedObject processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error;
-
-// Performs the actual work of deserialization. This method is also invoked when
-// processing relationships, to create a new adapter (if needed) to handle them.
-//
-// `processedObjects` is a dictionary mapping NSManagedObjects to the MTLModels
-// that have been created so far. It should remain alive for the full process
-// of deserializing the top-level managed object.
-+ (id)modelOfClass:(Class)modelClass fromManagedObject:(NSManagedObject *)managedObject processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error;
-
-// Invoked from
-// +managedObjectFromModel:insertingIntoContext:processedObjects:error: after
-// the receiver's properties have been initialized.
-- (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error;
-
-// Performs the actual work of serialization. This method is also invoked when
-// processing relationships, to create a new adapter (if needed) to handle them.
-//
-// `processedObjects` is a dictionary mapping MTLModels to the NSManagedObjects
-// that have been created so far. It should remain alive for the full process
-// of serializing the top-level MTLModel.
-+ (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error;
-
-// Looks up the NSValueTransformer that should be used for any attribute that
-// corresponds the given property key.
-//
-// key - The property key to transform from or to. This argument must not be nil.
-//
-// Returns a transformer to use, or nil to not transform the property.
-- (NSValueTransformer *)entityAttributeTransformerForKey:(NSString *)key;
-
-// Looks up the managed object key that corresponds to the given key.
-//
-// key - The property key to retrieve the corresponding managed object key for.
-//       This argument must not be nil.
-//
-// Returns a key to use, or nil to omit the property from managed object
-// serialization.
-- (NSString *)managedObjectKeyForKey:(NSString *)key;
-
-// Looks at propertyKeysForManagedObjectUniquing and forms an NSPredicate
-// using the uniquing keys and the provided model.
-- (NSPredicate *)uniquingPredicateForModel:(MTLModel<MTLManagedObjectSerializing> *)model;
-
-@end
-
-@implementation MTLManagedObjectAdapter
-
-#pragma mark Lifecycle
-
-- (id)init {
-	NSAssert(NO, @"%@ should not be initialized using -init", self.class);
-	return nil;
-}
-
-- (id)initWithModelClass:(Class)modelClass {
-	NSParameterAssert(modelClass != nil);
-
-	self = [super init];
-	if (self == nil) return nil;
-
-	_modelClass = modelClass;
-	_managedObjectKeysByPropertyKey = [[modelClass managedObjectKeysByPropertyKey] copy];
-
-	if ([modelClass respondsToSelector:@selector(relationshipModelClassesByPropertyKey)]) {
-		_relationshipModelClassesByPropertyKey = [[modelClass relationshipModelClassesByPropertyKey] copy];
-	}
-
-	return self;
-}
-
-#pragma mark Serialization
-
-- (id)modelFromManagedObject:(NSManagedObject *)managedObject processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
-	NSParameterAssert(managedObject != nil);
-	NSParameterAssert(processedObjects != nil);
-
-	NSEntityDescription *entity = managedObject.entity;
-	NSAssert(entity != nil, @"%@ returned a nil +entity", managedObject);
-
-	NSManagedObjectContext *context = managedObject.managedObjectContext;
-
-	NSDictionary *managedObjectProperties = entity.propertiesByName;
-	MTLModel *model = [[self.modelClass alloc] init];
-
-	// Pre-emptively consider this object processed, so that we don't get into
-	// any cycles when processing its relationships.
-	CFDictionaryAddValue(processedObjects, (__bridge void *)managedObject, (__bridge void *)model);
-
-	BOOL (^setValueForKey)(NSString *, id) = ^(NSString *key, id value) {
-		// Mark this as being autoreleased, because validateValue may return
-		// a new object to be stored in this variable (and we don't want ARC to
-		// double-free or leak the old or new values).
-		__autoreleasing id replaceableValue = value;
-		if (![model validateValue:&replaceableValue forKey:key error:error]) return NO;
-
-		[model setValue:replaceableValue forKey:key];
-		return YES;
-	};
-
-	for (NSString *propertyKey in [self.modelClass propertyKeys]) {
-		NSString *managedObjectKey = [self managedObjectKeyForKey:propertyKey];
-		if (managedObjectKey == nil) continue;
-
-		BOOL (^deserializeAttribute)(NSAttributeDescription *) = ^(NSAttributeDescription *attributeDescription) {
-			id value = performInContext(context, ^{
-				return [managedObject valueForKey:managedObjectKey];
-			});
-
-			NSValueTransformer *attributeTransformer = [self entityAttributeTransformerForKey:propertyKey];
-			if (attributeTransformer != nil) value = [attributeTransformer reverseTransformedValue:value];
-
-			return setValueForKey(propertyKey, value);
-		};
-
-		BOOL (^deserializeRelationship)(NSRelationshipDescription *) = ^(NSRelationshipDescription *relationshipDescription) {
-			Class nestedClass = self.relationshipModelClassesByPropertyKey[propertyKey];
-			if (nestedClass == nil) {
-				[NSException raise:NSInvalidArgumentException format:@"No class specified for decoding relationship at key \"%@\" in managed object %@", managedObjectKey, managedObject];
-			}
-
-			if ([relationshipDescription isToMany]) {
-				id models = performInContext(context, ^ id {
-					id relationshipCollection = [managedObject valueForKey:managedObjectKey];
-					NSMutableArray *models = [NSMutableArray arrayWithCapacity:[relationshipCollection count]];
-
-					for (NSManagedObject *nestedObject in relationshipCollection) {
-						MTLModel *model = [self.class modelOfClass:nestedClass fromManagedObject:nestedObject processedObjects:processedObjects error:error];
-						if (model == nil) return nil;
-						
-						[models addObject:model];
-					}
-
-					return models;
-				});
-
-				if (models == nil) return NO;
-				if (![relationshipDescription isOrdered]) models = [NSSet setWithArray:models];
-
-				return setValueForKey(propertyKey, models);
-			} else {
-				NSManagedObject *nestedObject = performInContext(context, ^{
-					return [managedObject valueForKey:managedObjectKey];
-				});
-
-				if (nestedObject == nil) return YES;
-
-				MTLModel *model = [self.class modelOfClass:nestedClass fromManagedObject:nestedObject processedObjects:processedObjects error:error];
-				if (model == nil) return NO;
-
-				return setValueForKey(propertyKey, model);
-			}
-		};
-
-		BOOL (^deserializeProperty)(NSPropertyDescription *) = ^(NSPropertyDescription *propertyDescription) {
-			if (propertyDescription == nil) {
-				if (error != NULL) {
-					NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"No property by name \"%@\" exists on the entity.", @""), managedObjectKey];
-
-					NSDictionary *userInfo = @{
-						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not deserialize managed object", @""),
-						NSLocalizedFailureReasonErrorKey: failureReason,
-					};
-
-					*error = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorInvalidManagedObjectKey userInfo:userInfo];
-				}
-
-				return NO;
-			}
-
-			// Jump through some hoops to avoid referencing classes directly.
-			NSString *propertyClassName = NSStringFromClass(propertyDescription.class);
-			if ([propertyClassName isEqual:@"NSAttributeDescription"]) {
-				return deserializeAttribute((id)propertyDescription);
-			} else if ([propertyClassName isEqual:@"NSRelationshipDescription"]) {
-				return deserializeRelationship((id)propertyDescription);
-			} else {
-				if (error != NULL) {
-					NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"Property descriptions of class %@ are unsupported.", @""), propertyClassName];
-
-					NSDictionary *userInfo = @{
-						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not deserialize managed object", @""),
-						NSLocalizedFailureReasonErrorKey: failureReason,
-					};
-
-					*error = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorUnsupportedManagedObjectPropertyType userInfo:userInfo];
-				}
-
-				return NO;
-			}
-		};
-
-		if (!deserializeProperty(managedObjectProperties[managedObjectKey])) return nil;
-	}
-
-	return model;
-}
-
-+ (id)modelOfClass:(Class)modelClass fromManagedObject:(NSManagedObject *)managedObject error:(NSError **)error {
-	NSSet *propertyKeys = [modelClass propertyKeys];
-
-	for (NSString *mappedPropertyKey in [modelClass managedObjectKeysByPropertyKey]) {
-		if ([propertyKeys containsObject:mappedPropertyKey]) continue;
-
-		if (error != NULL) {
-			NSDictionary *userInfo = @{
-				NSLocalizedDescriptionKey: NSLocalizedString(@"Invalid entity attribute mapping", nil),
-				NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"%1$@ could not be parsed because its entity attribute mapping contains illegal property keys.", nil), modelClass]
-			};
-
-			*error = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorInvalidManagedObjectMapping userInfo:userInfo];
-		}
-
-		return nil;
-	}
-
-	CFMutableDictionaryRef processedObjects = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
-	if (processedObjects == NULL) return nil;
-
-	@onExit {
-		CFRelease(processedObjects);
-	};
-
-	return [self modelOfClass:modelClass fromManagedObject:managedObject processedObjects:processedObjects error:error];
-}
-
-+ (id)modelOfClass:(Class)modelClass fromManagedObject:(NSManagedObject *)managedObject processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
-	NSParameterAssert(modelClass != nil);
-	NSParameterAssert(processedObjects != nil);
-
-	if (managedObject == nil) return nil;
-
-	const void *existingModel = CFDictionaryGetValue(processedObjects, (__bridge void *)managedObject);
-	if (existingModel != NULL) {
-		return (__bridge id)existingModel;
-	}
-
-	if ([modelClass respondsToSelector:@selector(classForDeserializingManagedObject:)]) {
-		modelClass = [modelClass classForDeserializingManagedObject:managedObject];
-		if (modelClass == nil) {
-			if (error != NULL) {
-				NSDictionary *userInfo = @{
-					NSLocalizedDescriptionKey: NSLocalizedString(@"Could not deserialize managed object", @""),
-					NSLocalizedFailureReasonErrorKey: NSLocalizedString(@"No model class could be found to deserialize the object.", @"")
-				};
-
-				*error = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorNoClassFound userInfo:userInfo];
-			}
-
-			return nil;
-		}
-	}
-
-	MTLManagedObjectAdapter *adapter = [[self alloc] initWithModelClass:modelClass];
-	return [adapter modelFromManagedObject:managedObject processedObjects:processedObjects error:error];
-}
-
-- (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
-	NSParameterAssert(model != nil);
-	NSParameterAssert(context != nil);
-	NSParameterAssert(processedObjects != nil);
-
-	NSString *entityName = [model.class managedObjectEntityName];
-	NSAssert(entityName != nil, @"%@ returned a nil +managedObjectEntityName", model.class);
-
-	Class entityDescriptionClass = NSClassFromString(@"NSEntityDescription");
-	NSAssert(entityDescriptionClass != nil, @"CoreData.framework must be linked to use MTLManagedObjectAdapter");
-
-	Class fetchRequestClass = NSClassFromString(@"NSFetchRequest");
-	NSAssert(fetchRequestClass != nil, @"CoreData.framework must be linked to use MTLManagedObjectAdapter");
-
-	// If a uniquing predicate is provided, perform a fetch request to guarantee a unique managed object.
-	__block NSManagedObject *managedObject = nil;
-	NSPredicate *uniquingPredicate = [self uniquingPredicateForModel:model];
-
-	if (uniquingPredicate != nil) {
-		__block NSError *fetchRequestError = nil;
-		__block BOOL encountedError = NO;
-		managedObject = performInContext(context, ^ id {
-			NSFetchRequest *fetchRequest = [[fetchRequestClass alloc] init];
-			fetchRequest.entity = [entityDescriptionClass entityForName:entityName inManagedObjectContext:context];
-			fetchRequest.predicate = uniquingPredicate;
-			fetchRequest.returnsObjectsAsFaults = NO;
-			fetchRequest.fetchLimit = 1;
-
-			NSArray *results = [context executeFetchRequest:fetchRequest error:&fetchRequestError];
-
-			if (results == nil) {
-				encountedError = YES;
-				if (error != NULL) {
-					NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"Failed to fetch a managed object for uniqing predicate \"%@\".", @""), uniquingPredicate];
-					
-					NSDictionary *userInfo = @{
-						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not serialize managed object", @""),
-						NSLocalizedFailureReasonErrorKey: failureReason,
-					};
-					
-					fetchRequestError = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorUniqueFetchRequestFailed userInfo:userInfo];
-				}
-				
-				return nil;
-			}
-
-			return results.mtl_firstObject;
-		});
-
-		if (encountedError && error != NULL) {
-			*error = fetchRequestError;
-			return nil;
-		}
-	}
-
-	if (managedObject == nil) {
-		managedObject = [entityDescriptionClass insertNewObjectForEntityForName:entityName inManagedObjectContext:context];
-	} else {
-		// Our CoreData store already has data for this model, we need to merge
-		[self mergeValuesOfModel:model forKeysFromManagedObject:managedObject];
-	}
-
-	if (managedObject == nil) {
-		if (error != NULL) {
-			NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"Failed to initialize a managed object from entity named \"%@\".", @""), entityName];
-
-			NSDictionary *userInfo = @{
-				NSLocalizedDescriptionKey: NSLocalizedString(@"Could not serialize managed object", @""),
-				NSLocalizedFailureReasonErrorKey: failureReason,
-			};
-
-			*error = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorInitializationFailed userInfo:userInfo];
-		}
-
-		return nil;
-	}
-
-	// Assign all errors to this variable to work around a memory problem.
-	//
-	// See https://github.com/github/Mantle/pull/120 for more context.
-	__block NSError *tmpError;
-
-	// Pre-emptively consider this object processed, so that we don't get into
-	// any cycles when processing its relationships.
-	CFDictionaryAddValue(processedObjects, (__bridge void *)model, (__bridge void *)managedObject);
-
-	NSDictionary *dictionaryValue = model.dictionaryValue;
-	NSDictionary *managedObjectProperties = managedObject.entity.propertiesByName;
-
-	[dictionaryValue enumerateKeysAndObjectsUsingBlock:^(NSString *propertyKey, id value, BOOL *stop) {
-		NSString *managedObjectKey = [self managedObjectKeyForKey:propertyKey];
-		if (managedObjectKey == nil) return;
-		if ([value isEqual:NSNull.null]) value = nil;
-
-		BOOL (^serializeAttribute)(NSAttributeDescription *) = ^(NSAttributeDescription *attributeDescription) {
-			// Mark this as being autoreleased, because validateValue may return
-			// a new object to be stored in this variable (and we don't want ARC to
-			// double-free or leak the old or new values).
-			__autoreleasing id transformedValue = value;
-
-			NSValueTransformer *attributeTransformer = [self entityAttributeTransformerForKey:propertyKey];
-			if (attributeTransformer != nil) transformedValue = [attributeTransformer transformedValue:transformedValue];
-
-			if (![managedObject validateValue:&transformedValue forKey:managedObjectKey error:&tmpError]) return NO;
-			[managedObject setValue:transformedValue forKey:managedObjectKey];
-
-			return YES;
-		};
-
-		NSManagedObject * (^objectForRelationshipFromModel)(id) = ^ id (id model) {
-			if (![model isKindOfClass:MTLModel.class] || ![model conformsToProtocol:@protocol(MTLManagedObjectSerializing)]) {
-				NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"Property of class %@ cannot be encoded into an NSManagedObject.", @""), [model class]];
-
-				NSDictionary *userInfo = @{
-					NSLocalizedDescriptionKey: NSLocalizedString(@"Could not serialize managed object", @""),
-					NSLocalizedFailureReasonErrorKey: failureReason
-				};
-
-				tmpError = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorUnsupportedRelationshipClass userInfo:userInfo];
-
-				return nil;
-			}
-
-			return [self.class managedObjectFromModel:model insertingIntoContext:context processedObjects:processedObjects error:&tmpError];
-		};
-
-		BOOL (^serializeRelationship)(NSRelationshipDescription *) = ^(NSRelationshipDescription *relationshipDescription) {
-			if (value == nil) return YES;
-
-			if ([relationshipDescription isToMany]) {
-				if (![value conformsToProtocol:@protocol(NSFastEnumeration)]) {
-					NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"Property of class %@ cannot be encoded into a to-many relationship.", @""), [value class]];
-
-					NSDictionary *userInfo = @{
-						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not serialize managed object", @""),
-						NSLocalizedFailureReasonErrorKey: failureReason
-					};
-
-					tmpError = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorUnsupportedRelationshipClass userInfo:userInfo];
-
-					return NO;
-				}
-
-				id relationshipCollection;
-				if ([relationshipDescription isOrdered]) {
-					relationshipCollection = [NSMutableOrderedSet orderedSet];
-				} else {
-					relationshipCollection = [NSMutableSet set];
-				}
-
-				for (MTLModel *model in value) {
-					NSManagedObject *nestedObject = objectForRelationshipFromModel(model);
-					if (nestedObject == nil) return NO;
-
-					[relationshipCollection addObject:nestedObject];
-				}
-
-				[managedObject setValue:relationshipCollection forKey:managedObjectKey];
-			} else {
-				NSManagedObject *nestedObject = objectForRelationshipFromModel(value);
-				if (nestedObject == nil) return NO;
-
-				[managedObject setValue:nestedObject forKey:managedObjectKey];
-			}
-
-			return YES;
-		};
-
-		BOOL (^serializeProperty)(NSPropertyDescription *) = ^(NSPropertyDescription *propertyDescription) {
-			if (propertyDescription == nil) {
-				NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"No property by name \"%@\" exists on the entity.", @""), managedObjectKey];
-
-				NSDictionary *userInfo = @{
-					NSLocalizedDescriptionKey: NSLocalizedString(@"Could not serialize managed object", @""),
-					NSLocalizedFailureReasonErrorKey: failureReason
-				};
-
-				tmpError = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorInvalidManagedObjectKey userInfo:userInfo];
-
-				return NO;
-			}
-
-			// Jump through some hoops to avoid referencing classes directly.
-			NSString *propertyClassName = NSStringFromClass(propertyDescription.class);
-			if ([propertyClassName isEqual:@"NSAttributeDescription"]) {
-				return serializeAttribute((id)propertyDescription);
-			} else if ([propertyClassName isEqual:@"NSRelationshipDescription"]) {
-				return serializeRelationship((id)propertyDescription);
-			} else {
-				NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"Property descriptions of class %@ are unsupported.", @""), propertyClassName];
-
-				NSDictionary *userInfo = @{
-					NSLocalizedDescriptionKey: NSLocalizedString(@"Could not serialize managed object", @""),
-					NSLocalizedFailureReasonErrorKey: failureReason
-				};
-
-				tmpError = [NSError errorWithDomain:MTLManagedObjectAdapterErrorDomain code:MTLManagedObjectAdapterErrorUnsupportedManagedObjectPropertyType userInfo:userInfo];
-
-				return NO;
-			}
-		};
-		
-		if (!serializeProperty(managedObjectProperties[managedObjectKey])) {
-			performInContext(context, ^ id {
-				[context deleteObject:managedObject];
-				return nil;
-			});
-
-			managedObject = nil;
-			*stop = YES;
-		}
-	}];
-
-	if (managedObject != nil && ![managedObject validateForInsert:&tmpError]) {
-		managedObject = performInContext(context, ^ id {
-			[context deleteObject:managedObject];
-			return nil;
-		});
-	}
-
-	if (error != NULL) {
-		*error = tmpError;
-	}
-
-	return managedObject;
-}
-
-+ (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context error:(NSError **)error {
-	CFDictionaryKeyCallBacks keyCallbacks = kCFTypeDictionaryKeyCallBacks;
-
-	// Compare MTLModel keys using pointer equality, not -isEqual:.
-	keyCallbacks.equal = NULL;
-
-	CFMutableDictionaryRef processedObjects = CFDictionaryCreateMutable(NULL, 0, &keyCallbacks, &kCFTypeDictionaryValueCallBacks);
-	if (processedObjects == NULL) return nil;
-
-	@onExit {
-		CFRelease(processedObjects);
-	};
-
-	return [self managedObjectFromModel:model insertingIntoContext:context processedObjects:processedObjects error:error];
-}
-
-+ (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
-	NSParameterAssert(model != nil);
-	NSParameterAssert(context != nil);
-	NSParameterAssert(processedObjects != nil);
-
-	const void *existingManagedObject = CFDictionaryGetValue(processedObjects, (__bridge void *)model);
-	if (existingManagedObject != NULL) {
-		return (__bridge id)existingManagedObject;
-	}
-
-	MTLManagedObjectAdapter *adapter = [[self alloc] initWithModelClass:model.class];
-	return [adapter managedObjectFromModel:model insertingIntoContext:context processedObjects:processedObjects error:error];
-}
-
-- (NSValueTransformer *)entityAttributeTransformerForKey:(NSString *)key {
-	NSParameterAssert(key != nil);
-
-	SEL selector = MTLSelectorWithKeyPattern(key, "EntityAttributeTransformer");
-	if ([self.modelClass respondsToSelector:selector]) {
-		IMP imp = [self.modelClass methodForSelector:selector];
-		NSValueTransformer * (*function)(id, SEL) = (__typeof__(function))imp;
-		NSValueTransformer *transformer = function(self.modelClass, selector);
-		return transformer;
-	}
-
-	if ([self.modelClass respondsToSelector:@selector(entityAttributeTransformerForKey:)]) {
-		return [self.modelClass entityAttributeTransformerForKey:key];
-	}
-
-	return nil;
-}
-
-- (NSString *)managedObjectKeyForKey:(NSString *)key {
-	NSParameterAssert(key != nil);
-
-	id managedObjectKey = self.managedObjectKeysByPropertyKey[key];
-	if ([managedObjectKey isEqual:NSNull.null]) return nil;
-
-	if (managedObjectKey == nil) {
-		return key;
-	} else {
-		return managedObjectKey;
-	}
-}
-
-- (void)mergeValueOfModel:(MTLModel<MTLManagedObjectSerializing> *)model forKey:(NSString *)key fromManagedObject:(NSManagedObject *)managedObject {
-	[model mergeValueForKey:key fromManagedObject:managedObject];
-}
-
-- (void)mergeValuesOfModel:(MTLModel<MTLManagedObjectSerializing> *)model forKeysFromManagedObject:(NSManagedObject *)managedObject {
-	if ([model respondsToSelector:@selector(mergeValuesForKeysFromManagedObject:)]) {
-		[model mergeValuesForKeysFromManagedObject:managedObject];
-	} else if ([model respondsToSelector:@selector(mergeValueForKey:fromManagedObject:)]) {
-		[[model.class managedObjectKeysByPropertyKey] enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *managedObjectKey, BOOL *stop) {
-			[self mergeValueOfModel:model forKey:key fromManagedObject:managedObject];
-		}];
-	}
-}
-
-- (NSPredicate *)uniquingPredicateForModel:(MTLModel<MTLManagedObjectSerializing> *)model {
-	if (![self.modelClass respondsToSelector:@selector(propertyKeysForManagedObjectUniquing)]) return nil;
-
-	NSSet *propertyKeys = [self.modelClass propertyKeysForManagedObjectUniquing];
-
-	if (propertyKeys == nil) return nil;
-
-	NSAssert(propertyKeys.count > 0, @"+propertyKeysForManagedObjectUniquing must not be empty.");
-
-	NSMutableArray *subpredicates = [NSMutableArray array];
-	for (NSString *propertyKey in propertyKeys) {
-		NSString *managedObjectKey = [self managedObjectKeyForKey:propertyKey];
-
-		NSAssert(managedObjectKey != nil, @"%@ must map to a managed object key.", propertyKey);
-
-		id transformedValue = [model valueForKeyPath:propertyKey];
-
-		NSValueTransformer *attributeTransformer = [self entityAttributeTransformerForKey:propertyKey];
-		if (attributeTransformer != nil) transformedValue = [attributeTransformer transformedValue:transformedValue];
-
-		NSPredicate *subpredicate = [NSPredicate predicateWithFormat:@"%K == %@", managedObjectKey, transformedValue];
-		[subpredicates addObject:subpredicate];
-	}
-	
-	return [NSCompoundPredicate andPredicateWithSubpredicates:subpredicates];
-}
-
-@end

Mantle/MTLModel+NSCoding.h

@@ -8,121 +8,121 @@
 
 #import "MTLModel.h"
 
-// Defines how a MTLModel property key should be encoded into an archive.
-//
-// MTLModelEncodingBehaviorExcluded      - The property should never be encoded.
-// MTLModelEncodingBehaviorUnconditional - The property should always be
-//                                         encoded.
-// MTLModelEncodingBehaviorConditional   - The object should be encoded only
-//                                         if unconditionally encoded elsewhere.
-//                                         This should only be used for object
-//                                         properties.
+/// Defines how a MTLModel property key should be encoded into an archive.
+///
+/// MTLModelEncodingBehaviorExcluded      - The property should never be encoded.
+/// MTLModelEncodingBehaviorUnconditional - The property should always be
+///                                         encoded.
+/// MTLModelEncodingBehaviorConditional   - The object should be encoded only
+///                                         if unconditionally encoded elsewhere.
+///                                         This should only be used for object
+///                                         properties.
 typedef enum : NSUInteger {
     MTLModelEncodingBehaviorExcluded = 0,
     MTLModelEncodingBehaviorUnconditional,
     MTLModelEncodingBehaviorConditional,
 } MTLModelEncodingBehavior;
 
-// Implements default archiving and unarchiving behaviors for MTLModel.
+/// Implements default archiving and unarchiving behaviors for MTLModel.
 @interface MTLModel (NSCoding) <NSCoding>
 
-// Initializes the receiver from an archive.
-//
-// This will decode the original +modelVersion of the archived object, then
-// invoke -decodeValueForKey:withCoder:modelVersion: for each of the receiver's
-// +propertyKeys.
-//
-// Returns an initialized model object, or nil if a decoding error occurred.
+/// Initializes the receiver from an archive.
+///
+/// This will decode the original +modelVersion of the archived object, then
+/// invoke -decodeValueForKey:withCoder:modelVersion: for each of the receiver's
+/// +propertyKeys.
+///
+/// Returns an initialized model object, or nil if a decoding error occurred.
 - (id)initWithCoder:(NSCoder *)coder;
 
-// Archives the receiver using the given coder.
-//
-// This will encode the receiver's +modelVersion, then the receiver's properties
-// according to the behaviors specified in +encodingBehaviorsByPropertyKey.
+/// Archives the receiver using the given coder.
+///
+/// This will encode the receiver's +modelVersion, then the receiver's properties
+/// according to the behaviors specified in +encodingBehaviorsByPropertyKey.
 - (void)encodeWithCoder:(NSCoder *)coder;
 
-// Determines how the +propertyKeys of the class are encoded into an archive.
-// The values of this dictionary should be boxed MTLModelEncodingBehavior
-// values.
-//
-// Any keys not present in the dictionary will be excluded from the archive.
-//
-// Subclasses overriding this method should combine their values with those of
-// `super`.
-//
-// Returns a dictionary mapping the receiver's +propertyKeys to default encoding
-// behaviors. If a property is an object with `weak` semantics, the default
-// behavior is MTLModelEncodingBehaviorConditional; otherwise, the default is
-// MTLModelEncodingBehaviorUnconditional.
+/// Determines how the +propertyKeys of the class are encoded into an archive.
+/// The values of this dictionary should be boxed MTLModelEncodingBehavior
+/// values.
+///
+/// Any keys not present in the dictionary will be excluded from the archive.
+///
+/// Subclasses overriding this method should combine their values with those of
+/// `super`.
+///
+/// Returns a dictionary mapping the receiver's +propertyKeys to default encoding
+/// behaviors. If a property is an object with `weak` semantics, the default
+/// behavior is MTLModelEncodingBehaviorConditional; otherwise, the default is
+/// MTLModelEncodingBehaviorUnconditional.
 + (NSDictionary *)encodingBehaviorsByPropertyKey;
 
-// Determines the classes that are allowed to be decoded for each of the
-// receiver's properties when using <NSSecureCoding>. The values of this
-// dictionary should be NSArrays of Class objects.
-//
-// If any encodable keys (as determined by +encodingBehaviorsByPropertyKey) are
-// not present in the dictionary, an exception will be thrown during secure
-// encoding or decoding.
-//
-// Subclasses overriding this method should combine their values with those of
-// `super`.
-//
-// Returns a dictionary mapping the receiver's encodable keys (as determined by
-// +encodingBehaviorsByPropertyKey) to default allowed classes, based on the
-// type that each property is declared as. If type of an encodable property
-// cannot be determined (e.g., it is declared as `id`), it will be omitted from
-// the dictionary, and subclasses must provide a valid value to prevent an
-// exception being thrown during encoding/decoding.
+/// Determines the classes that are allowed to be decoded for each of the
+/// receiver's properties when using <NSSecureCoding>. The values of this
+/// dictionary should be NSArrays of Class objects.
+///
+/// If any encodable keys (as determined by +encodingBehaviorsByPropertyKey) are
+/// not present in the dictionary, an exception will be thrown during secure
+/// encoding or decoding.
+///
+/// Subclasses overriding this method should combine their values with those of
+/// `super`.
+///
+/// Returns a dictionary mapping the receiver's encodable keys (as determined by
+/// +encodingBehaviorsByPropertyKey) to default allowed classes, based on the
+/// type that each property is declared as. If type of an encodable property
+/// cannot be determined (e.g., it is declared as `id`), it will be omitted from
+/// the dictionary, and subclasses must provide a valid value to prevent an
+/// exception being thrown during encoding/decoding.
 + (NSDictionary *)allowedSecureCodingClassesByPropertyKey;
 
-// Decodes the value of the given property key from an archive.
-//
-// By default, this method looks for a `-decode<Key>WithCoder:modelVersion:`
-// method on the receiver, and invokes it if found.
-//
-// If the custom method is not implemented and `coder` does not require secure
-// coding, `-[NSCoder decodeObjectForKey:]` will be invoked with the given
-// `key`.
-//
-// If the custom method is not implemented and `coder` requires secure coding,
-// `-[NSCoder decodeObjectOfClasses:forKey:]` will be invoked with the
-// information from +allowedSecureCodingClassesByPropertyKey and the given `key`. The
-// receiver must conform to <NSSecureCoding> for this to work correctly.
-//
-// key          - The property key to decode the value for. This argument cannot
-//                be nil.
-// coder        - The NSCoder representing the archive being decoded. This
-//                argument cannot be nil.
-// modelVersion - The version of the original model object that was encoded.
-//
-// Returns the decoded and boxed value, or nil if the key was not present.
+/// Decodes the value of the given property key from an archive.
+///
+/// By default, this method looks for a `-decode<Key>WithCoder:modelVersion:`
+/// method on the receiver, and invokes it if found.
+///
+/// If the custom method is not implemented and `coder` does not require secure
+/// coding, `-[NSCoder decodeObjectForKey:]` will be invoked with the given
+/// `key`.
+///
+/// If the custom method is not implemented and `coder` requires secure coding,
+/// `-[NSCoder decodeObjectOfClasses:forKey:]` will be invoked with the
+/// information from +allowedSecureCodingClassesByPropertyKey and the given `key`. The
+/// receiver must conform to <NSSecureCoding> for this to work correctly.
+///
+/// key          - The property key to decode the value for. This argument cannot
+///                be nil.
+/// coder        - The NSCoder representing the archive being decoded. This
+///                argument cannot be nil.
+/// modelVersion - The version of the original model object that was encoded.
+///
+/// Returns the decoded and boxed value, or nil if the key was not present.
 - (id)decodeValueForKey:(NSString *)key withCoder:(NSCoder *)coder modelVersion:(NSUInteger)modelVersion;
 
-// The version of this MTLModel subclass.
-//
-// This version number is saved in archives so that later model changes can be
-// made backwards-compatible with old versions.
-//
-// Subclasses should override this method to return a higher version number
-// whenever a breaking change is made to the model.
-//
-// Returns 0.
+/// The version of this MTLModel subclass.
+///
+/// This version number is saved in archives so that later model changes can be
+/// made backwards-compatible with old versions.
+///
+/// Subclasses should override this method to return a higher version number
+/// whenever a breaking change is made to the model.
+///
+/// Returns 0.
 + (NSUInteger)modelVersion;
 
 @end
 
-// This method must be overridden to support archives created by older versions
-// of Mantle (before the `MTLModel+NSCoding` interface existed).
+/// This method must be overridden to support archives created by older versions
+/// of Mantle (before the `MTLModel+NSCoding` interface existed).
 @interface MTLModel (OldArchiveSupport)
 
-// Converts an archived external representation to a dictionary suitable for
-// passing to -initWithDictionary:.
-//
-// externalRepresentation - The decoded external representation of the receiver.
-// fromVersion            - The model version at the time the external
-//                          representation was encoded.
-//
-// Returns nil by default, indicating that conversion failed.
+/// Converts an archived external representation to a dictionary suitable for
+/// passing to -initWithDictionary:.
+///
+/// externalRepresentation - The decoded external representation of the receiver.
+/// fromVersion            - The model version at the time the external
+///                          representation was encoded.
+///
+/// Returns nil by default, indicating that conversion failed.
 + (NSDictionary *)dictionaryValueFromArchivedExternalRepresentation:(NSDictionary *)externalRepresentation version:(NSUInteger)fromVersion;
 
 @end

Mantle/MTLModel+NSCoding.m

@@ -7,10 +7,9 @@
 //
 
 #import "MTLModel+NSCoding.h"
-#import "MTLEXTRuntimeExtensions.h"
-#import "MTLEXTScope.h"
+#import <Mantle/EXTRuntimeExtensions.h>
+#import <Mantle/EXTScope.h>
 #import "MTLReflection.h"
-#import <objc/runtime.h>
 
 // Used in archives to store the modelVersion of the archived instance.
 static NSString * const MTLModelVersionKey = @"MTLModelVersion";

Mantle/MTLModel.h

@@ -8,118 +8,172 @@
 
 #import <Foundation/Foundation.h>
 
-// An abstract base class for model objects, using reflection to provide
-// sensible default behaviors.
-//
-// The default implementations of <NSCopying>, -hash, and -isEqual: make use of
-// the +propertyKeys method.
-@interface MTLModel : NSObject <NSCopying>
+/// Defines a property's storage behavior, which affects how it will be copied,
+/// compared, and persisted.
+///
+/// MTLPropertyStorageNone       - This property is not included in -description,
+///                                -hash, or anything else.
+/// MTLPropertyStorageTransitory - This property is included in one-off
+///                                operations like -copy and -dictionaryValue but
+///                                does not affect -isEqual: or -hash.
+///                                It may disappear at any time.
+/// MTLPropertyStoragePermanent  - The property is included in serialization
+///                                (like `NSCoding`) and equality, since it can
+///                                be expected to stick around.
+typedef enum : NSUInteger {
+    MTLPropertyStorageNone,
+    MTLPropertyStorageTransitory,
+    MTLPropertyStoragePermanent,
+} MTLPropertyStorage;
 
-// Returns a new instance of the receiver initialized using
-// -initWithDictionary:error:.
+/// This protocol defines the minimal interface that classes need to implement to
+/// interact with Mantle adapters.
+///
+/// It is intended for scenarios where inheriting from MTLModel is not feasible.
+/// However, clients are encouraged to subclass the MTLModel class if they can.
+///
+/// Clients that wish to implement their own adapters should target classes
+/// conforming to this protocol rather than subclasses of MTLModel to ensure
+/// maximum compatibility.
+@protocol MTLModel <NSObject, NSCopying>
+
+/// Initializes a new instance of the receiver using key-value coding, setting
+/// the keys and values in the given dictionary.
+///
+/// dictionaryValue - Property keys and values to set on the instance. Any NSNull
+///                   values will be converted to nil before being used. KVC
+///                   validation methods will automatically be invoked for all of
+///                   the properties given.
+/// error           - If not NULL, this may be set to any error that occurs
+///                   (like a KVC validation error).
+///
+/// Returns an initialized model object, or nil if validation failed.
 + (instancetype)modelWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error;
 
-// Initializes the receiver with default values.
-//
-// This is the designated initializer for this class.
-- (instancetype)init;
-
-// Initializes the receiver using key-value coding, setting the keys and values
-// in the given dictionary.
-//
-// Subclass implementations may override this method, calling the super
-// implementation, in order to perform further processing and initialization
-// after deserialization.
-//
-// dictionaryValue - Property keys and values to set on the receiver. Any NSNull
-//                   values will be converted to nil before being used. KVC
-//                   validation methods will automatically be invoked for all of
-//                   the properties given. If nil, this method is equivalent to
-//                   -init.
-// error           - If not NULL, this may be set to any error that occurs
-//                   (like a KVC validation error).
-//
-// Returns an initialized model object, or nil if validation failed.
-- (instancetype)initWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error;
-
-// Returns the keys for all @property declarations, except for `readonly`
-// properties without ivars, or properties on MTLModel itself.
-+ (NSSet *)propertyKeys;
-
-// A dictionary representing the properties of the receiver.
-//
-// The default implementation combines the values corresponding to all
-// +propertyKeys into a dictionary, with any nil values represented by NSNull.
-//
-// This property must never be nil.
+/// A dictionary representing the properties of the receiver.
+///
+/// Combines the values corresponding to all +propertyKeys into a dictionary,
+/// with any nil values represented by NSNull.
+///
+/// This property must never be nil.
 @property (nonatomic, copy, readonly) NSDictionary *dictionaryValue;
 
-// Merges the value of the given key on the receiver with the value of the same
-// key from the given model object, giving precedence to the other model object.
-//
-// By default, this method looks for a `-merge<Key>FromModel:` method on the
-// receiver, and invokes it if found. If not found, and `model` is not nil, the
-// value for the given key is taken from `model`.
-- (void)mergeValueForKey:(NSString *)key fromModel:(MTLModel *)model;
+/// Initializes the receiver using key-value coding, setting the keys and values
+/// in the given dictionary.
+///
+/// Subclass implementations may override this method, calling the super
+/// implementation, in order to perform further processing and initialization
+/// after deserialization.
+///
+/// dictionaryValue - Property keys and values to set on the receiver. Any NSNull
+///                   values will be converted to nil before being used. KVC
+///                   validation methods will automatically be invoked for all of
+///                   the properties given. If nil, this method is equivalent to
+///                   -init.
+/// error           - If not NULL, this may be set to any error that occurs
+///                   (like a KVC validation error).
+///
+/// Returns an initialized model object, or nil if validation failed.
+- (instancetype)initWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error;
 
-// Merges the values of the given model object into the receiver, using
-// -mergeValueForKey:fromModel: for each key in +propertyKeys.
-//
-// `model` must be an instance of the receiver's class or a subclass thereof.
-- (void)mergeValuesForKeysFromModel:(MTLModel *)model;
+/// Merges the value of the given key on the receiver with the value of the same
+/// key from the given model object, giving precedence to the other model object.
+- (void)mergeValueForKey:(NSString *)key fromModel:(id<MTLModel>)model;
 
-// Compares the receiver with another object for equality.
-//
-// The default implementation is equivalent to comparing both models'
-// -dictionaryValue.
-//
-// Note that this may lead to infinite loops if the receiver holds a circular
-// reference to another MTLModel and both use the default behavior.
-// It is recommended to override -isEqual: in this scenario.
-- (BOOL)isEqual:(id)object;
+/// Returns the keys for all @property declarations, except for `readonly`
+/// properties without ivars, or properties on MTLModel itself.
++ (NSSet *)propertyKeys;
 
-// A string that describes the contents of the receiver.
-//
-// The default implementation is based on the receiver's class and its
-// -dictionaryValue.
-//
-// Note that this may lead to infinite loops if the receiver holds a circular
-// reference to another MTLModel and both use the default behavior.
-// It is recommended to override -description in this scenario.
-- (NSString *)description;
-
-@end
-
-// Implements validation logic for MTLModel.
-@interface MTLModel (Validation)
-
-// Validates the model.
-//
-// The default implementation simply invokes -validateValue:forKey:error: with
-// all +propertyKeys and their current value. If -validateValue:forKey:error:
-// returns a new value, the property is set to that new value.
-//
-// error - If not NULL, this may be set to any error that occurs during
-//         validation
-//
-// Returns YES if the model is valid, or NO if the validation failed.
+/// Validates the model.
+///
+/// error - If not NULL, this may be set to any error that occurs during
+///         validation
+///
+/// Returns YES if the model is valid, or NO if the validation failed.
 - (BOOL)validate:(NSError **)error;
 
 @end
 
-@interface MTLModel (Unavailable)
+/// An abstract base class for model objects, using reflection to provide
+/// sensible default behaviors.
+///
+/// The default implementations of <NSCopying>, -hash, and -isEqual: make use of
+/// the +propertyKeys method.
+@interface MTLModel : NSObject <MTLModel>
 
-+ (instancetype)modelWithDictionary:(NSDictionary *)dictionaryValue __attribute__((deprecated("Replaced by +modelWithDictionary:error:")));
-- (instancetype)initWithDictionary:(NSDictionary *)dictionaryValue __attribute__((deprecated("Replaced by -initWithDictionary:error:")));
+/// Initializes the receiver using key-value coding, setting the keys and values
+/// in the given dictionary.
+///
+/// dictionaryValue - Property keys and values to set on the receiver. Any NSNull
+///                   values will be converted to nil before being used. KVC
+///                   validation methods will automatically be invoked for all of
+///                   the properties given. If nil, this method is equivalent to
+///                   -init.
+/// error           - If not NULL, this may be set to any error that occurs
+///                   (like a KVC validation error).
+///
+/// Returns an initialized model object, or nil if validation failed.
+- (instancetype)initWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error;
 
-+ (instancetype)modelWithExternalRepresentation:(NSDictionary *)externalRepresentation __attribute__((deprecated("Replaced by -[MTLJSONAdapter initWithJSONDictionary:modelClass:]")));
-- (instancetype)initWithExternalRepresentation:(NSDictionary *)externalRepresentation __attribute__((deprecated("Replaced by -[MTLJSONAdapter initWithJSONDictionary:modelClass:]")));
+/// Initializes the receiver with default values.
+///
+/// This is the designated initializer for this class.
+- (instancetype)init;
 
-@property (nonatomic, copy, readonly) NSDictionary *externalRepresentation __attribute__((deprecated("Replaced by MTLJSONAdapter.JSONDictionary")));
+/// By default, this method looks for a `-merge<Key>FromModel:` method on the
+/// receiver, and invokes it if found. If not found, and `model` is not nil, the
+/// value for the given key is taken from `model`.
+- (void)mergeValueForKey:(NSString *)key fromModel:(id<MTLModel>)model;
 
-+ (NSDictionary *)externalRepresentationKeyPathsByPropertyKey __attribute__((deprecated("Replaced by +JSONKeyPathsByPropertyKey in <MTLJSONSerializing>")));
-+ (NSValueTransformer *)transformerForKey:(NSString *)key __attribute__((deprecated("Replaced by +JSONTransformerForKey: in <MTLJSONSerializing>")));
+/// Merges the values of the given model object into the receiver, using
+/// -mergeValueForKey:fromModel: for each key in +propertyKeys.
+///
+/// `model` must be an instance of the receiver's class or a subclass thereof.
+- (void)mergeValuesForKeysFromModel:(id<MTLModel>)model;
 
-+ (NSDictionary *)migrateExternalRepresentation:(NSDictionary *)externalRepresentation fromVersion:(NSUInteger)fromVersion __attribute__((deprecated("Replaced by -decodeValueForKey:withCoder:modelVersion:")));
+/// The storage behavior of a given key.
+///
+/// The default implementation returns MTLPropertyStorageNone for properties that
+/// are readonly and not backed by an instance variable and
+/// MTLPropertyStoragePermanent otherwise.
+///
+/// Subclasses can use this method to prevent MTLModel from resolving circular
+/// references by returning MTLPropertyStorageTransitory.
+///
+/// Returns the storage behavior for a given key on the receiver.
++ (MTLPropertyStorage)storageBehaviorForPropertyWithKey:(NSString *)propertyKey;
+
+/// Compares the receiver with another object for equality.
+///
+/// The default implementation is equivalent to comparing all properties of both
+/// models for which +storageBehaviorForPropertyWithKey: returns
+/// MTLPropertyStoragePermanent.
+///
+/// Returns YES if the two models are considered equal, NO otherwise.
+- (BOOL)isEqual:(id)object;
+
+/// A string that describes the contents of the receiver.
+///
+/// The default implementation is based on the receiver's class and all its
+/// properties for which +storageBehaviorForPropertyWithKey: returns
+/// MTLPropertyStoragePermanent.
+- (NSString *)description;
+
+@end
+
+/// Implements validation logic for MTLModel.
+@interface MTLModel (Validation)
+
+/// Validates the model.
+///
+/// The default implementation simply invokes -validateValue:forKey:error: with
+/// all +propertyKeys and their current value. If -validateValue:forKey:error:
+/// returns a new value, the property is set to that new value.
+///
+/// error - If not NULL, this may be set to any error that occurs during
+///         validation
+///
+/// Returns YES if the model is valid, or NO if the validation failed.
+- (BOOL)validate:(NSError **)error;
 
 @end

Mantle/MTLModel.m

@@ -8,19 +8,22 @@
 
 #import "NSError+MTLModelException.h"
 #import "MTLModel.h"
-#import "MTLEXTRuntimeExtensions.h"
-#import "MTLEXTScope.h"
+#import <Mantle/EXTRuntimeExtensions.h>
+#import <Mantle/EXTScope.h>
 #import "MTLReflection.h"
 #import <objc/runtime.h>
 
-// This coupling is needed for backwards compatibility in MTLModel's deprecated
-// methods.
-#import "MTLJSONAdapter.h"
-#import "MTLModel+NSCoding.h"
-
 // Used to cache the reflection performed in +propertyKeys.
 static void *MTLModelCachedPropertyKeysKey = &MTLModelCachedPropertyKeysKey;
 
+// Associated in +generateAndCachePropertyKeys with a set of all transitory
+// property keys.
+static void *MTLModelCachedTransitoryPropertyKeysKey = &MTLModelCachedTransitoryPropertyKeysKey;
+
+// Associated in +generateAndCachePropertyKeys with a set of all permanent
+// property keys.
+static void *MTLModelCachedPermanentPropertyKeysKey = &MTLModelCachedPermanentPropertyKeysKey;
+
 // Validates a value for an object and sets it if necessary.
 //
 // obj         - The object for which the value is being validated. This value
@@ -67,6 +70,18 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 
 @interface MTLModel ()
 
+// Inspects all properties of returned by +propertyKeys using
+// +storageBehaviorForPropertyWithKey and caches the results.
++ (void)generateAndCacheStorageBehaviors;
+
+// Returns a set of all property keys for which
+// +storageBehaviorForPropertyWithKey returned MTLPropertyStorageTransitory.
++ (NSSet *)transitoryPropertyKeys;
+
+// Returns a set of all property keys for which
+// +storageBehaviorForPropertyWithKey returned MTLPropertyStoragePermanent.
++ (NSSet *)permanentPropertyKeys;
+
 // Enumerates all properties of the receiver's class hierarchy, starting at the
 // receiver, and continuing up until (but not including) MTLModel.
 //
@@ -80,6 +95,31 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 
 #pragma mark Lifecycle
 
++ (void)generateAndCacheStorageBehaviors {
+	NSMutableSet *transitoryKeys = [NSMutableSet set];
+	NSMutableSet *permanentKeys = [NSMutableSet set];
+
+	for (NSString *propertyKey in self.propertyKeys) {
+		switch ([self storageBehaviorForPropertyWithKey:propertyKey]) {
+			case MTLPropertyStorageNone:
+				break;
+
+			case MTLPropertyStorageTransitory:
+				[transitoryKeys addObject:propertyKey];
+				break;
+
+			case MTLPropertyStoragePermanent:
+				[permanentKeys addObject:propertyKey];
+				break;
+		}
+	}
+
+	// It doesn't really matter if we replace another thread's work, since we do
+	// it atomically and the result should be the same.
+	objc_setAssociatedObject(self, MTLModelCachedTransitoryPropertyKeysKey, transitoryKeys, OBJC_ASSOCIATION_COPY);
+	objc_setAssociatedObject(self, MTLModelCachedPermanentPropertyKeysKey, permanentKeys, OBJC_ASSOCIATION_COPY);
+}
+
 + (instancetype)modelWithDictionary:(NSDictionary *)dictionary error:(NSError **)error {
 	return [[self alloc] initWithDictionary:dictionary error:error];
 }
@@ -98,7 +138,7 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 		// a new object to be stored in this variable (and we don't want ARC to
 		// double-free or leak the old or new values).
 		__autoreleasing id value = [dictionary objectForKey:key];
-	
+
 		if ([value isEqual:NSNull.null]) value = nil;
 
 		BOOL success = MTLValidateAndSetValue(self, key, value, YES, error);
@@ -139,15 +179,11 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 	NSMutableSet *keys = [NSMutableSet set];
 
 	[self enumeratePropertiesUsingBlock:^(objc_property_t property, BOOL *stop) {
-		mtl_propertyAttributes *attributes = mtl_copyPropertyAttributes(property);
-		@onExit {
-			free(attributes);
-		};
-
-		if (attributes->readonly && attributes->ivar == NULL) return;
-
 		NSString *key = @(property_getName(property));
-		[keys addObject:key];
+
+		if ([self storageBehaviorForPropertyWithKey:key] != MTLPropertyStorageNone) {
+			 [keys addObject:key];
+		}
 	}];
 
 	// It doesn't really matter if we replace another thread's work, since we do
@@ -157,13 +193,64 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 	return keys;
 }
 
++ (NSSet *)transitoryPropertyKeys {
+	NSSet *transitoryPropertyKeys = objc_getAssociatedObject(self, MTLModelCachedTransitoryPropertyKeysKey);
+
+	if (transitoryPropertyKeys == nil) {
+		[self generateAndCacheStorageBehaviors];
+		transitoryPropertyKeys = objc_getAssociatedObject(self, MTLModelCachedTransitoryPropertyKeysKey);
+	}
+
+	return transitoryPropertyKeys;
+}
+
++ (NSSet *)permanentPropertyKeys {
+	NSSet *permanentPropertyKeys = objc_getAssociatedObject(self, MTLModelCachedPermanentPropertyKeysKey);
+
+	if (permanentPropertyKeys == nil) {
+		[self generateAndCacheStorageBehaviors];
+		permanentPropertyKeys = objc_getAssociatedObject(self, MTLModelCachedPermanentPropertyKeysKey);
+	}
+
+	return permanentPropertyKeys;
+}
+
 - (NSDictionary *)dictionaryValue {
-	return [self dictionaryWithValuesForKeys:self.class.propertyKeys.allObjects];
+	NSSet *keys = [self.class.transitoryPropertyKeys setByAddingObjectsFromSet:self.class.permanentPropertyKeys];
+
+	return [self dictionaryWithValuesForKeys:keys.allObjects];
+}
+
++ (MTLPropertyStorage)storageBehaviorForPropertyWithKey:(NSString *)propertyKey {
+	objc_property_t property = class_getProperty(self.class, propertyKey.UTF8String);
+
+	if (property == NULL) return MTLPropertyStorageNone;
+
+	mtl_propertyAttributes *attributes = mtl_copyPropertyAttributes(property);
+	@onExit {
+		free(attributes);
+	};
+	
+	BOOL hasGetter = [self instancesRespondToSelector:attributes->getter];
+	BOOL hasSetter = [self instancesRespondToSelector:attributes->setter];
+	if (!attributes->dynamic && attributes->ivar == NULL && !hasGetter && !hasSetter) {
+		return MTLPropertyStorageNone;
+	} else if (attributes->readonly && attributes->ivar == NULL) {
+		if ([self isEqual:MTLModel.class]) {
+			return MTLPropertyStorageNone;
+		} else {
+			// Check superclass in case the subclass redeclares a property that
+			// falls through
+			return [self.superclass storageBehaviorForPropertyWithKey:propertyKey];
+		}
+	} else {
+		return MTLPropertyStoragePermanent;
+	}
 }
 
 #pragma mark Merging
 
-- (void)mergeValueForKey:(NSString *)key fromModel:(MTLModel *)model {
+- (void)mergeValueForKey:(NSString *)key fromModel:(NSObject<MTLModel> *)model {
 	NSParameterAssert(key != nil);
 
 	SEL selector = MTLSelectorWithCapitalizedKeyPattern("merge", key, "FromModel:");
@@ -176,12 +263,13 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 	}
 
 	IMP imp = [self methodForSelector:selector];
-	void (*function)(id, SEL, MTLModel *) = (__typeof__(function))imp;
+	void (*function)(id, SEL, id<MTLModel>) = (__typeof__(function))imp;
 	function(self, selector, model);
 }
 
-- (void)mergeValuesForKeysFromModel:(MTLModel *)model {
+- (void)mergeValuesForKeysFromModel:(id<MTLModel>)model {
 	NSSet *propertyKeys = model.class.propertyKeys;
+
 	for (NSString *key in self.class.propertyKeys) {
 		if (![propertyKeys containsObject:key]) continue;
 
@@ -205,19 +293,23 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 #pragma mark NSCopying
 
 - (instancetype)copyWithZone:(NSZone *)zone {
-	return [[self.class allocWithZone:zone] initWithDictionary:self.dictionaryValue error:NULL];
+	MTLModel *copy = [[self.class allocWithZone:zone] init];
+	[copy setValuesForKeysWithDictionary:self.dictionaryValue];
+	return copy;
 }
 
 #pragma mark NSObject
 
 - (NSString *)description {
-	return [NSString stringWithFormat:@"<%@: %p> %@", self.class, self, self.dictionaryValue];
+	NSDictionary *permanentProperties = [self dictionaryWithValuesForKeys:self.class.permanentPropertyKeys.allObjects];
+
+	return [NSString stringWithFormat:@"<%@: %p> %@", self.class, self, permanentProperties];
 }
 
 - (NSUInteger)hash {
 	NSUInteger value = 0;
 
-	for (NSString *key in self.class.propertyKeys) {
+	for (NSString *key in self.class.permanentPropertyKeys) {
 		value ^= [[self valueForKey:key] hash];
 	}
 
@@ -228,7 +320,7 @@ static BOOL MTLValidateAndSetValue(id obj, NSString *key, id value, BOOL forceUp
 	if (self == model) return YES;
 	if (![model isMemberOfClass:self.class]) return NO;
 
-	for (NSString *key in self.class.propertyKeys) {
+	for (NSString *key in self.class.permanentPropertyKeys) {
 		id selfValue = [self valueForKey:key];
 		id modelValue = [model valueForKey:key];
 

Mantle/MTLReflection.h

@@ -8,24 +8,24 @@
 
 #import <Foundation/Foundation.h>
 
-// Creates a selector from a key and a constant string.
-//
-// key    - The key to insert into the generated selector. This key should be in
-//          its natural case.
-// suffix - A string to append to the key as part of the selector.
-//
-// Returns a selector, or NULL if the input strings cannot form a valid
-// selector.
+/// Creates a selector from a key and a constant string.
+///
+/// key    - The key to insert into the generated selector. This key should be in
+///          its natural case.
+/// suffix - A string to append to the key as part of the selector.
+///
+/// Returns a selector, or NULL if the input strings cannot form a valid
+/// selector.
 SEL MTLSelectorWithKeyPattern(NSString *key, const char *suffix) __attribute__((pure, nonnull(1, 2)));
 
-// Creates a selector from a key and a constant prefix and suffix.
-//
-// prefix - A string to prepend to the key as part of the selector.
-// key    - The key to insert into the generated selector. This key should be in
-//          its natural case, and will have its first letter capitalized when
-//          inserted.
-// suffix - A string to append to the key as part of the selector.
-//
-// Returns a selector, or NULL if the input strings cannot form a valid
-// selector.
+/// Creates a selector from a key and a constant prefix and suffix.
+///
+/// prefix - A string to prepend to the key as part of the selector.
+/// key    - The key to insert into the generated selector. This key should be in
+///          its natural case, and will have its first letter capitalized when
+///          inserted.
+/// suffix - A string to append to the key as part of the selector.
+///
+/// Returns a selector, or NULL if the input strings cannot form a valid
+/// selector.
 SEL MTLSelectorWithCapitalizedKeyPattern(const char *prefix, NSString *key, const char *suffix) __attribute__((pure, nonnull(1, 2, 3)));

Mantle/MTLTransformerErrorHandling.h

@@ -0,0 +1,66 @@
+//
+//  MTLTransformerErrorHandling.h
+//  Mantle
+//
+//  Created by Robert Böhnke on 10/6/13.
+//  Copyright (c) 2013 GitHub. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+/// The domain for errors originating from the MTLTransformerErrorHandling
+/// protocol.
+///
+/// Transformers conforming to this protocol are expected to use this error
+/// domain if the transformation fails.
+extern NSString * const MTLTransformerErrorHandlingErrorDomain;
+
+/// Used to indicate that the input value was illegal.
+///
+/// Transformers conforming to this protocol are expected to use this error code
+/// if the transformation fails due to an invalid input value.
+extern const NSInteger MTLTransformerErrorHandlingErrorInvalidInput;
+
+/// Associated with the invalid input value.
+///
+/// Transformers conforming to this protocol are expected to associate this key
+/// with the invalid input in the userInfo dictionary.
+extern NSString * const MTLTransformerErrorHandlingInputValueErrorKey;
+
+/// This protocol can be implemented by NSValueTransformer subclasses to
+/// communicate errors that occur during transformation.
+@protocol MTLTransformerErrorHandling <NSObject>
+@required
+
+/// Transforms a value, returning any error that occurred during transformation.
+///
+/// value   - The value to transform.
+/// success - If not NULL, this will be set to a boolean indicating whether the
+///           transformation was successful.
+/// error   - If not NULL, this may be set to an error that occurs during
+///           transforming the value.
+///
+/// Returns the result of the transformation which may be nil. Clients should
+/// inspect the success parameter to decide how to proceed with the result.
+- (id)transformedValue:(id)value success:(BOOL *)success error:(NSError **)error;
+
+@optional
+
+/// Reverse-transforms a value, returning any error that occurred during
+/// transformation.
+///
+/// Transformers conforming to this protocol are expected to implemented this
+/// method if they support reverse transformation.
+///
+/// value   - The value to transform.
+/// success - If not NULL, this will be set to a boolean indicating whether the
+///           transformation was successful.
+/// error   - If not NULL, this may be set to an error that occurs during
+///           transforming the value.
+///
+/// Returns the result of the reverse transformation which may be nil. Clients
+/// should inspect the success parameter to decide how to proceed with the
+/// result.
+- (id)reverseTransformedValue:(id)value success:(BOOL *)success error:(NSError **)error;
+
+@end

Mantle/MTLTransformerErrorHandling.m

@@ -0,0 +1,15 @@
+//
+//  MTLTransformerErrorHandling.h
+//  Mantle
+//
+//  Created by Robert Böhnke on 10/6/13.
+//  Copyright (c) 2013 GitHub. All rights reserved.
+//
+
+#import "MTLTransformerErrorHandling.h"
+
+NSString * const MTLTransformerErrorHandlingErrorDomain = @"MTLTransformerErrorHandlingErrorDomain";
+
+const NSInteger MTLTransformerErrorHandlingErrorInvalidInput = 1;
+
+NSString * const MTLTransformerErrorHandlingInputValueErrorKey = @"MTLTransformerErrorHandlingInputValueErrorKey";

Mantle/MTLValueTransformer.h

@@ -8,22 +8,45 @@
 
 #import <Foundation/Foundation.h>
 
-typedef id (^MTLValueTransformerBlock)(id);
+#import "MTLTransformerErrorHandling.h"
 
-//
-// A value transformer supporting block-based transformation.
-//
-@interface MTLValueTransformer : NSValueTransformer
+/// A block that represents a transformation.
+///
+/// value   - The value to transform.
+/// success - The block must set this parameter to indicate whether the
+///           transformation was successful.
+///           MTLValueTransformer will always call this block with *success
+///           initialized to YES.
+/// error   - If not NULL, this may be set to an error that occurs during
+///           transforming the value.
+///
+/// Returns the result of the transformation, which may be nil.
+typedef id (^MTLValueTransformerBlock)(id value, BOOL *success, NSError **error);
 
-// Returns a transformer which transforms values using the given block. Reverse
-// transformations will not be allowed.
-+ (instancetype)transformerWithBlock:(MTLValueTransformerBlock)transformationBlock;
+///
+/// A value transformer supporting block-based transformation.
+///
+@interface MTLValueTransformer : NSValueTransformer <MTLTransformerErrorHandling>
 
-// Returns a transformer which transforms values using the given block, for
-// forward or reverse transformations.
-+ (instancetype)reversibleTransformerWithBlock:(MTLValueTransformerBlock)transformationBlock;
+/// Returns a transformer which transforms values using the given block. Reverse
+/// transformations will not be allowed.
++ (instancetype)transformerUsingForwardBlock:(MTLValueTransformerBlock)transformation;
 
-// Returns a transformer which transforms values using the given blocks.
-+ (instancetype)reversibleTransformerWithForwardBlock:(MTLValueTransformerBlock)forwardBlock reverseBlock:(MTLValueTransformerBlock)reverseBlock;
+/// Returns a transformer which transforms values using the given block, for
+/// forward or reverse transformations.
++ (instancetype)transformerUsingReversibleBlock:(MTLValueTransformerBlock)transformation;
+
+/// Returns a transformer which transforms values using the given blocks.
++ (instancetype)transformerUsingForwardBlock:(MTLValueTransformerBlock)forwardTransformation reverseBlock:(MTLValueTransformerBlock)reverseTransformation;
+
+@end
+
+@interface MTLValueTransformer (Deprecated)
+
++ (NSValueTransformer *)transformerWithBlock:(id (^)(id))transformationBlock __attribute__((deprecated("Replaced by +transformerUsingForwardBlock:")));
+
++ (NSValueTransformer *)reversibleTransformerWithBlock:(id (^)(id))transformationBlock __attribute__((deprecated("Replaced by +transformerUsingReversibleBlock:")));
+
++ (NSValueTransformer *)reversibleTransformerWithForwardBlock:(id (^)(id))forwardBlock reverseBlock:(id (^)(id))reverseBlock __attribute__((deprecated("Replaced by +transformerUsingForwardBlock:reverseBlock:")));
 
 @end

Mantle/MTLValueTransformer.m

@@ -26,15 +26,15 @@
 
 #pragma mark Lifecycle
 
-+ (instancetype)transformerWithBlock:(MTLValueTransformerBlock)transformationBlock {
-	return [[self alloc] initWithForwardBlock:transformationBlock reverseBlock:nil];
++ (instancetype)transformerUsingForwardBlock:(MTLValueTransformerBlock)forwardBlock {
+	return [[self alloc] initWithForwardBlock:forwardBlock reverseBlock:nil];
 }
 
-+ (instancetype)reversibleTransformerWithBlock:(MTLValueTransformerBlock)transformationBlock {
-	return [self reversibleTransformerWithForwardBlock:transformationBlock reverseBlock:transformationBlock];
++ (instancetype)transformerUsingReversibleBlock:(MTLValueTransformerBlock)reversibleBlock {
+	return [self transformerUsingForwardBlock:reversibleBlock reverseBlock:reversibleBlock];
 }
 
-+ (instancetype)reversibleTransformerWithForwardBlock:(MTLValueTransformerBlock)forwardBlock reverseBlock:(MTLValueTransformerBlock)reverseBlock {
++ (instancetype)transformerUsingForwardBlock:(MTLValueTransformerBlock)forwardBlock reverseBlock:(MTLValueTransformerBlock)reverseBlock {
 	return [[MTLReversibleValueTransformer alloc] initWithForwardBlock:forwardBlock reverseBlock:reverseBlock];
 }
 
@@ -57,11 +57,26 @@
 }
 
 + (Class)transformedValueClass {
-	return [NSObject class];
+	return NSObject.class;
 }
 
 - (id)transformedValue:(id)value {
-	return self.forwardBlock(value);
+	NSError *error = nil;
+	BOOL success = YES;
+
+	return self.forwardBlock(value, &success, &error);
+}
+
+- (id)transformedValue:(id)value success:(BOOL *)outerSuccess error:(NSError **)outerError {
+	NSError *error = nil;
+	BOOL success = YES;
+
+	id transformedValue = self.forwardBlock(value, &success, &error);
+
+	if (outerSuccess != NULL) *outerSuccess = success;
+	if (outerError != NULL) *outerError = error;
+
+	return transformedValue;
 }
 
 @end
@@ -82,7 +97,54 @@
 }
 
 - (id)reverseTransformedValue:(id)value {
-	return self.reverseBlock(value);
+	NSError *error = nil;
+	BOOL success = YES;
+
+	return self.reverseBlock(value, &success, &error);
+}
+
+- (id)reverseTransformedValue:(id)value success:(BOOL *)outerSuccess error:(NSError **)outerError {
+	NSError *error = nil;
+	BOOL success = YES;
+
+	id transformedValue = self.reverseBlock(value, &success, &error);
+
+	if (outerSuccess != NULL) *outerSuccess = success;
+	if (outerError != NULL) *outerError = error;
+
+	return transformedValue;
 }
 
 @end
+
+
+@implementation MTLValueTransformer (Deprecated)
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-implementations"
+
++ (instancetype)transformerWithBlock:(id (^)(id))transformationBlock {
+	return [self transformerUsingForwardBlock:^(id value, BOOL *success, NSError **error) {
+		return transformationBlock(value);
+	}];
+}
+
++ (instancetype)reversibleTransformerWithBlock:(id (^)(id))transformationBlock {
+	return [self transformerUsingReversibleBlock:^(id value, BOOL *success, NSError **error) {
+		return transformationBlock(value);
+	}];
+}
+
++ (instancetype)reversibleTransformerWithForwardBlock:(id (^)(id))forwardBlock reverseBlock:(id (^)(id))reverseBlock {
+	return [self
+		transformerUsingForwardBlock:^(id value, BOOL *success, NSError **error) {
+			return forwardBlock(value);
+		}
+		reverseBlock:^(id value, BOOL *success, NSError **error) {
+			return reverseBlock(value);
+		}];
+}
+
+#pragma clang diagnostic pop
+
+@end

Mantle/Mantle.h

@@ -15,12 +15,13 @@ FOUNDATION_EXPORT double MantleVersionNumber;
 FOUNDATION_EXPORT const unsigned char MantleVersionString[];
 
 #import <Mantle/MTLJSONAdapter.h>
-#import <Mantle/MTLManagedObjectAdapter.h>
 #import <Mantle/MTLModel.h>
 #import <Mantle/MTLModel+NSCoding.h>
 #import <Mantle/MTLValueTransformer.h>
+#import <Mantle/MTLTransformerErrorHandling.h>
 #import <Mantle/NSArray+MTLManipulationAdditions.h>
 #import <Mantle/NSDictionary+MTLManipulationAdditions.h>
+#import <Mantle/NSDictionary+MTLMappingAdditions.h>
 #import <Mantle/NSObject+MTLComparisonAdditions.h>
 #import <Mantle/NSValueTransformer+MTLInversionAdditions.h>
 #import <Mantle/NSValueTransformer+MTLPredefinedTransformerAdditions.h>

Mantle/NSArray+MTLManipulationAdditions.h

@@ -10,19 +10,19 @@
 
 @interface NSArray (MTLManipulationAdditions)
 
-// The first object in the array or nil if the array is empty.
-// Forwards to `firstObject` which has been first declared in iOS7, but works with iOS4/10.6.
+/// The first object in the array or nil if the array is empty.
+/// Forwards to `firstObject` which has been first declared in iOS7, but works with iOS4/10.6.
 @property (nonatomic, readonly, strong) id mtl_firstObject;
 
-// Returns a new array without all instances of the given object.
+/// Returns a new array without all instances of the given object.
 - (NSArray *)mtl_arrayByRemovingObject:(id)object;
 
-// Returns a new array without the first object. If the array is empty, it
-// returns the empty array.
+/// Returns a new array without the first object. If the array is empty, it
+/// returns the empty array.
 - (NSArray *)mtl_arrayByRemovingFirstObject;
 
-// Returns a new array without the last object. If the array is empty, it
-// returns the empty array.
+/// Returns a new array without the last object. If the array is empty, it
+/// returns the empty array.
 - (NSArray *)mtl_arrayByRemovingLastObject;
 
 @end

Mantle/NSDictionary+MTLJSONKeyPath.h

@@ -0,0 +1,27 @@
+//
+//  NSDictionary+MTLJSONKeyPath.h
+//  Mantle
+//
+//  Created by Robert Böhnke on 19/03/14.
+//  Copyright (c) 2014 GitHub. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface NSDictionary (MTLJSONKeyPath)
+
+/// Looks up the value of a key path in the receiver.
+///
+/// JSONKeyPath - The key path that should be resolved. Every element along this
+///               key path needs to be an instance of NSDictionary for the
+///               resolving to be successful.
+/// success     - If not NULL, this will be set to a boolean indicating whether
+///               the key path was resolved successfully.
+/// error       - If not NULL, this may be set to an error that occurs during
+///               resolving the value.
+///
+/// Returns the value for the key path which may be nil. Clients should inspect
+/// the success parameter to decide how to proceed with the result.
+- (id)mtl_valueForJSONKeyPath:(NSString *)JSONKeyPath success:(BOOL *)success error:(NSError **)error;
+
+@end

Mantle/NSDictionary+MTLJSONKeyPath.m

@@ -0,0 +1,47 @@
+//
+//  NSDictionary+MTLJSONKeyPath.m
+//  Mantle
+//
+//  Created by Robert Böhnke on 19/03/14.
+//  Copyright (c) 2014 GitHub. All rights reserved.
+//
+
+#import "NSDictionary+MTLJSONKeyPath.h"
+
+#import "MTLJSONAdapter.h"
+
+@implementation NSDictionary (MTLJSONKeyPath)
+
+- (id)mtl_valueForJSONKeyPath:(NSString *)JSONKeyPath success:(BOOL *)success error:(NSError **)error {
+	NSArray *components = [JSONKeyPath componentsSeparatedByString:@"."];
+
+	id result = self;
+	for (NSString *component in components) {
+		// Check the result before resolving the key path component to not
+		// affect the last value of the path.
+		if (result == nil || result == NSNull.null) break;
+
+		if (![result isKindOfClass:NSDictionary.class]) {
+			if (error != NULL) {
+				NSDictionary *userInfo = @{
+					NSLocalizedDescriptionKey: NSLocalizedString(@"Invalid JSON dictionary", @""),
+					NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"JSON key path %1$@ could not resolved because an incompatible JSON dictionary was supplied: \"%2$@\"", @""), JSONKeyPath, self]
+				};
+
+				*error = [NSError errorWithDomain:MTLJSONAdapterErrorDomain code:MTLJSONAdapterErrorInvalidJSONDictionary userInfo:userInfo];
+			}
+
+			if (success != NULL) *success = NO;
+
+			return nil;
+		}
+
+		result = result[component];
+	}
+
+	if (success != NULL) *success = YES;
+
+	return result;
+}
+
+@end

Mantle/NSDictionary+MTLManipulationAdditions.h

@@ -10,16 +10,22 @@
 
 @interface NSDictionary (MTLManipulationAdditions)
 
-// Merges the keys and values from the given dictionary into the receiver. If
-// both the receiver and `dictionary` have a given key, the value from
-// `dictionary` is used.
-//
-// Returns a new dictionary containing the entries of the receiver combined with
-// those of `dictionary`.
+/// Merges the keys and values from the given dictionary into the receiver. If
+/// both the receiver and `dictionary` have a given key, the value from
+/// `dictionary` is used.
+///
+/// Returns a new dictionary containing the entries of the receiver combined with
+/// those of `dictionary`.
 - (NSDictionary *)mtl_dictionaryByAddingEntriesFromDictionary:(NSDictionary *)dictionary;
 
-// Creates a new dictionary with all the entries for the given keys removed from
-// the receiver.
-- (NSDictionary *)mtl_dictionaryByRemovingEntriesWithKeys:(NSSet *)keys;
+/// Creates a new dictionary with all the entries for the given keys removed from
+/// the receiver.
+- (NSDictionary *)mtl_dictionaryByRemovingValuesForKeys:(NSArray *)keys;
+
+@end
+
+@interface NSDictionary (MTLManipulationAdditions_Deprecated)
+
+- (NSDictionary *)mtl_dictionaryByRemovingEntriesWithKeys:(NSSet *)keys __attribute__((deprecated("Replaced by -mtl_dictionaryByRemovingValuesForKeys:")));
 
 @end

Mantle/NSDictionary+MTLManipulationAdditions.m

@@ -16,10 +16,23 @@
 	return result;
 }
 
-- (NSDictionary *)mtl_dictionaryByRemovingEntriesWithKeys:(NSSet *)keys {
+- (NSDictionary *)mtl_dictionaryByRemovingValuesForKeys:(NSArray *)keys {
 	NSMutableDictionary *result = [self mutableCopy];
-	[result removeObjectsForKeys:keys.allObjects];
+	[result removeObjectsForKeys:keys];
 	return result;
 }
 
 @end
+
+@implementation NSDictionary (MTLManipulationAdditions_Deprecated)
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated"
+
+- (NSDictionary *)mtl_dictionaryByRemovingEntriesWithKeys:(NSSet *)keys {
+	return [self mtl_dictionaryByRemovingValuesForKeys:keys.allObjects];
+}
+
+#pragma clang diagnostic pop
+
+@end

Mantle/NSDictionary+MTLMappingAdditions.h

@@ -0,0 +1,21 @@
+//
+//  NSDictionary+MTLMappingAdditions.h
+//  Mantle
+//
+//  Created by Robert Böhnke on 10/31/13.
+//  Copyright (c) 2013 GitHub. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface NSDictionary (MTLMappingAdditions)
+
+/// Creates an identity mapping for serialization.
+///
+/// class - A subclass of MTLModel.
+///
+/// Returns a dictionary that maps all properties of the given class to
+/// themselves.
++ (NSDictionary *)mtl_identityPropertyMapWithModel:(Class)modelClass;
+
+@end

Mantle/NSDictionary+MTLMappingAdditions.m

@@ -0,0 +1,23 @@
+//
+//  NSDictionary+MTLMappingAdditions.m
+//  Mantle
+//
+//  Created by Robert Böhnke on 10/31/13.
+//  Copyright (c) 2013 GitHub. All rights reserved.
+//
+
+#import "MTLModel.h"
+
+#import "NSDictionary+MTLMappingAdditions.h"
+
+@implementation NSDictionary (MTLMappingAdditions)
+
++ (NSDictionary *)mtl_identityPropertyMapWithModel:(Class)modelClass {
+	NSCParameterAssert([modelClass conformsToProtocol:@protocol(MTLModel)]);
+
+	NSArray *propertyKeys = [modelClass propertyKeys].allObjects;
+
+	return [NSDictionary dictionaryWithObjects:propertyKeys forKeys:propertyKeys];
+}
+
+@end

Mantle/NSError+MTLModelException.h

@@ -10,14 +10,14 @@
 
 @interface NSError (MTLModelException)
 
-// Creates a new error for an exception that occured during updating an
-// MTLModel.
-//
-// exception - The exception that was thrown while updating the model.
-//             This argument must not be nil.
-//
-// Returns an error that takes its localized description and failure reason
-// from the exception.
+/// Creates a new error for an exception that occurred during updating an
+/// MTLModel.
+///
+/// exception - The exception that was thrown while updating the model.
+///             This argument must not be nil.
+///
+/// Returns an error that takes its localized description and failure reason
+/// from the exception.
 + (instancetype)mtl_modelErrorWithException:(NSException *)exception;
 
 @end

Mantle/NSObject+MTLComparisonAdditions.h

@@ -11,5 +11,5 @@
 
 #import <Foundation/Foundation.h>
 
-// Returns whether both objects are identical or equal via -isEqual:
+/// Returns whether both objects are identical or equal via -isEqual:
 BOOL MTLEqualObjects(id obj1, id obj2);

Mantle/NSValueTransformer+MTLInversionAdditions.h

@@ -10,12 +10,12 @@
 
 @interface NSValueTransformer (MTLInversionAdditions)
 
-// Flips the direction of the receiver's transformation, such that
-// -transformedValue: will become -reverseTransformedValue:, and vice-versa.
-//
-// The receiver must allow reverse transformation.
-//
-// Returns an inverted transformer.
+/// Flips the direction of the receiver's transformation, such that
+/// -transformedValue: will become -reverseTransformedValue:, and vice-versa.
+///
+/// The receiver must allow reverse transformation.
+///
+/// Returns an inverted transformer.
 - (NSValueTransformer *)mtl_invertedTransformer;
 
 @end

Mantle/NSValueTransformer+MTLInversionAdditions.m

@@ -7,6 +7,7 @@
 //
 
 #import "NSValueTransformer+MTLInversionAdditions.h"
+#import "MTLTransformerErrorHandling.h"
 #import "MTLValueTransformer.h"
 
 @implementation NSValueTransformer (MTLInversionAdditions)
@@ -14,11 +15,23 @@
 - (NSValueTransformer *)mtl_invertedTransformer {
 	NSParameterAssert(self.class.allowsReverseTransformation);
 
-	return [MTLValueTransformer reversibleTransformerWithForwardBlock:^(id value) {
-		return [self reverseTransformedValue:value];
-	} reverseBlock:^(id value) {
-		return [self transformedValue:value];
-	}];
+	if ([self conformsToProtocol:@protocol(MTLTransformerErrorHandling)]) {
+		NSParameterAssert([self respondsToSelector:@selector(reverseTransformedValue:success:error:)]);
+
+		id<MTLTransformerErrorHandling> errorHandlingSelf = (id)self;
+
+		return [MTLValueTransformer transformerUsingForwardBlock:^(id value, BOOL *success, NSError **error) {
+			return [errorHandlingSelf reverseTransformedValue:value success:success error:error];
+		} reverseBlock:^(id value, BOOL *success, NSError **error) {
+			return [errorHandlingSelf transformedValue:value success:success error:error];
+		}];
+	} else {
+		return [MTLValueTransformer transformerUsingForwardBlock:^(id value, BOOL *success, NSError **error) {
+			return [self reverseTransformedValue:value];
+		} reverseBlock:^(id value, BOOL *success, NSError **error) {
+			return [self transformedValue:value];
+		}];
+	}
 }
 
 @end

Mantle/NSValueTransformer+MTLPredefinedTransformerAdditions.h

@@ -8,77 +8,111 @@
 
 #import <Foundation/Foundation.h>
 
-// The name for a value transformer that converts strings into URLs and back.
+#import "MTLTransformerErrorHandling.h"
+
+/// The name for a value transformer that converts strings into URLs and back.
 extern NSString * const MTLURLValueTransformerName;
 
-// Ensure an NSNumber is backed by __NSCFBoolean/CFBooleanRef
-//
-// NSJSONSerialization, and likely other serialization libraries, ordinarily
-// serialize NSNumbers as numbers, and thus booleans would be serialized as
-// 0/1. The exception is when the NSNumber is backed by __NSCFBoolean, which,
-// though very much an implementation detail, is detected and serialized as a
-// proper boolean.
+/// The name for a value transformer that converts strings into NSUUIDs and back.
+extern NSString * const MTLUUIDValueTransformerName;
+
+/// Ensure an NSNumber is backed by __NSCFBoolean/CFBooleanRef
+///
+/// NSJSONSerialization, and likely other serialization libraries, ordinarily
+/// serialize NSNumbers as numbers, and thus booleans would be serialized as
+/// 0/1. The exception is when the NSNumber is backed by __NSCFBoolean, which,
+/// though very much an implementation detail, is detected and serialized as a
+/// proper boolean.
 extern NSString * const MTLBooleanValueTransformerName;
 
 @interface NSValueTransformer (MTLPredefinedTransformerAdditions)
 
-// Creates a reversible transformer to convert a JSON dictionary into a MTLModel
-// object, and vice-versa.
-//
-// modelClass - The MTLModel subclass to attempt to parse from the JSON. This
-//              class must conform to <MTLJSONSerializing>. This argument must
-//              not be nil.
-//
-// Returns a reversible transformer which uses MTLJSONAdapter for transforming
-// values back and forth.
-+ (NSValueTransformer *)mtl_JSONDictionaryTransformerWithModelClass:(Class)modelClass;
+/// An optionally reversible transformer which applies the given transformer to
+/// each element of an array.
+///
+/// transformer - The transformer to apply to each element. If the transformer
+///               is reversible, the transformer returned by this method will be
+///               reversible. This argument must not be nil.
+///
+/// Returns a transformer which applies a transformation to each element of an
+/// array.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_arrayMappingTransformerWithTransformer:(NSValueTransformer *)transformer;
 
-// Creates a reversible transformer to convert an array of JSON dictionaries
-// into an array of MTLModel objects, and vice-versa.
-//
-// modelClass - The MTLModel subclass to attempt to parse from each JSON
-//              dictionary. This class must conform to <MTLJSONSerializing>.
-//              This argument must not be nil.
-//
-// Returns a reversible transformer which uses MTLJSONAdapter for transforming
-// array elements back and forth.
-+ (NSValueTransformer *)mtl_JSONArrayTransformerWithModelClass:(Class)modelClass;
+/// A reversible value transformer to transform between the keys and objects of a
+/// dictionary.
+///
+/// dictionary          - The dictionary whose keys and values should be
+///                       transformed between. This argument must not be nil.
+/// defaultValue        - The result to fall back to, in case no key matching the
+///                       input value was found during a forward transformation.
+/// reverseDefaultValue - The result to fall back to, in case no value matching
+///                       the input value was found during a reverse
+///                       transformation.
+///
+/// Can for example be used for transforming between enum values and their string
+/// representation.
+///
+///   NSValueTransformer *valueTransformer = [NSValueTransformer mtl_valueMappingTransformerWithDictionary:@{
+///     @"foo": @(EnumDataTypeFoo),
+///     @"bar": @(EnumDataTypeBar),
+///   } defaultValue: @(EnumDataTypeUndefined) reverseDefaultValue: @"undefined"];
+///
+/// Returns a transformer which will map from keys to objects for forward
+/// transformations, and from objects to keys for reverse transformations.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_valueMappingTransformerWithDictionary:(NSDictionary *)dictionary defaultValue:(id)defaultValue reverseDefaultValue:(id)reverseDefaultValue;
 
-// A reversible value transformer to transform between the keys and objects of a
-// dictionary.
-//
-// dictionary          - The dictionary whose keys and values should be
-//                       transformed between. This argument must not be nil.
-// defaultValue        - The result to fall back to, in case no key matching the
-//                       input value was found during a forward transformation.
-// reverseDefaultValue - The result to fall back to, in case no value matching
-//                       the input value was found during a reverse
-//                       transformation.
-//
-// Can for example be used for transforming between enum values and their string
-// representation.
-//
-//   NSValueTransformer *valueTransformer = [NSValueTransformer mtl_valueMappingTransformerWithDictionary:@{
-//     @"foo": @(EnumDataTypeFoo),
-//     @"bar": @(EnumDataTypeBar),
-//   } defaultValue: @(EnumDataTypeUndefined) reverseDefaultValue: @"undefined"];
-//
-// Returns a transformer that will map from keys to values in dictionary
-// for forward transformation, and from values to keys for reverse
-// transformations. If no matching key or value can be found, the respective
-// default value is returned.
-+ (NSValueTransformer *)mtl_valueMappingTransformerWithDictionary:(NSDictionary *)dictionary defaultValue:(id)defaultValue reverseDefaultValue:(id)reverseDefaultValue;
+/// Returns a value transformer created by calling
+/// `+mtl_valueMappingTransformerWithDictionary:defaultValue:reverseDefaultValue:`
+/// with a default value of `nil` and a reverse default value of `nil`.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_valueMappingTransformerWithDictionary:(NSDictionary *)dictionary;
 
-// Returns a value transformer created by calling
-// `+mtl_valueMappingTransformerWithDictionary:defaultValue:reverseDefaultValue:`
-// with a default value of `nil` and a reverse default value of `nil`.
-+ (NSValueTransformer *)mtl_valueMappingTransformerWithDictionary:(NSDictionary *)dictionary;
-
-@end
-
-@interface NSValueTransformer (UnavailableMTLPredefinedTransformerAdditions)
-
-+ (NSValueTransformer *)mtl_externalRepresentationTransformerWithModelClass:(Class)modelClass __attribute__((deprecated("Replaced by +mtl_JSONDictionaryTransformerWithModelClass:")));
-+ (NSValueTransformer *)mtl_externalRepresentationArrayTransformerWithModelClass:(Class)modelClass __attribute__((deprecated("Replaced by +mtl_JSONArrayTransformerWithModelClass:")));
+/// A reversible value transformer to transform between a date and its string
+/// representation
+///
+/// dateFormat - The date format used by the date formatter (http://www.unicode.org/reports/tr35/tr35-31/tr35-dates.html#Date_Field_Symbol_Table)
+/// calendar   - The calendar used by the date formatter
+/// locale     - The locale used by the date formatter
+/// timeZone   - The time zone used by the date formatter
+///
+/// Returns a transformer which will map from strings to dates for forward
+/// transformations, and from dates to strings for reverse transformations.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_dateTransformerWithDateFormat:(NSString *)dateFormat calendar:(NSCalendar *)calendar locale:(NSLocale *)locale timeZone:(NSTimeZone *)timeZone defaultDate:(NSDate *)defaultDate;
+
+/// Returns a value transformer created by calling
+/// `+mtl_dateTransformerWithDateFormat:calendar:locale:timeZone:defaultDate:`
+/// with a calendar, locale, time zone and default date of `nil`.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_dateTransformerWithDateFormat:(NSString *)dateFormat locale:(NSLocale *)locale;
+
+/// A reversible value transformer to transform between a number and its string
+/// representation
+///
+/// numberStyle - The number style used by the number formatter
+///
+/// Returns a transformer which will map from strings to numbers for forward
+/// transformations, and from numbers to strings for reverse transformations.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_numberTransformerWithNumberStyle:(NSNumberFormatterStyle)numberStyle locale:(NSLocale *)locale;
+
+/// A reversible value transformer to transform between an object and its string
+/// representation
+///
+/// formatter   - The formatter used to perform the transformation
+/// objectClass - The class of object that the formatter operates on
+///
+/// Returns a transformer which will map from strings to objects for forward
+/// transformations, and from objects to strings for reverse transformations.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_transformerWithFormatter:(NSFormatter *)formatter forObjectClass:(Class)objectClass;
+
+/// A value transformer that errors if the transformed value are not of the given
+/// class.
+///
+/// class - The expected class. This argument must not be nil.
+///
+/// Returns a transformer which will return an error if the transformed in value
+/// is not a member of class. Otherwise, the value is simply passed through.
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_validatingTransformerForClass:(Class)modelClass;
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_JSONDictionaryTransformerWithModelClass:(Class)modelClass __attribute__((deprecated("Replaced by +[MTLJSONAdapter dictionaryTransformerWithModelClass:]")));
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_JSONArrayTransformerWithModelClass:(Class)modelClass __attribute__((deprecated("Replaced by +[MTLJSONAdapter arrayTransformerWithModelClass:]")));
 
 @end

Mantle/NSValueTransformer+MTLPredefinedTransformerAdditions.m

@@ -12,6 +12,7 @@
 #import "MTLValueTransformer.h"
 
 NSString * const MTLURLValueTransformerName = @"MTLURLValueTransformerName";
+NSString * const MTLUUIDValueTransformerName = @"MTLUUIDValueTransformerName";
 NSString * const MTLBooleanValueTransformerName = @"MTLBooleanValueTransformerName";
 
 @implementation NSValueTransformer (MTLPredefinedTransformerAdditions)
@@ -21,20 +22,132 @@ NSString * const MTLBooleanValueTransformerName = @"MTLBooleanValueTransformerNa
 + (void)load {
 	@autoreleasepool {
 		MTLValueTransformer *URLValueTransformer = [MTLValueTransformer
-			reversibleTransformerWithForwardBlock:^ id (NSString *str) {
-				if (![str isKindOfClass:NSString.class]) return nil;
-				return [NSURL URLWithString:str];
+			transformerUsingForwardBlock:^ id (NSString *str, BOOL *success, NSError **error) {
+				if (str == nil) return nil;
+
+				if (![str isKindOfClass:NSString.class]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert string to URL", @""),
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSString, got: %@.", @""), str],
+							MTLTransformerErrorHandlingInputValueErrorKey : str
+						};
+
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+
+				NSURL *result = [NSURL URLWithString:str];
+
+				if (result == nil) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert string to URL", @""),
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Input URL string %@ was malformed", @""), str],
+							MTLTransformerErrorHandlingInputValueErrorKey : str
+						};
+
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+
+				return result;
 			}
-			reverseBlock:^ id (NSURL *URL) {
-				if (![URL isKindOfClass:NSURL.class]) return nil;
+			reverseBlock:^ id (NSURL *URL, BOOL *success, NSError **error) {
+				if (URL == nil) return nil;
+
+				if (![URL isKindOfClass:NSURL.class]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert URL to string", @""),
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSURL, got: %@.", @""), URL],
+							MTLTransformerErrorHandlingInputValueErrorKey : URL
+						};
+
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
 				return URL.absoluteString;
 			}];
-		
+
 		[NSValueTransformer setValueTransformer:URLValueTransformer forName:MTLURLValueTransformerName];
 
+		MTLValueTransformer *UUIDValueTransformer = [MTLValueTransformer
+				transformerUsingForwardBlock:^id(NSString *string, BOOL *success, NSError **error) {
+					if (string == nil) return nil;
+					
+					if (![string isKindOfClass:NSString.class]) {
+						if (error) {
+							NSDictionary *userInfo = @{
+								NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert string to UUID", @""),
+								NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSString, got: %@.", @""), string],
+								MTLTransformerErrorHandlingInputValueErrorKey : string
+							};
+							*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+						}
+						*success = NO;
+						return nil;
+					}
+					
+					NSUUID *result = [[NSUUID alloc] initWithUUIDString:string];
+					
+					if (result == nil) {
+						if (error) {
+							NSDictionary *userInfo = @{
+								NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert string to UUID", @""),
+								NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Input UUID string %@ was malformed", @""), string],
+													   MTLTransformerErrorHandlingInputValueErrorKey : string
+							};
+							*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+						}
+						*success = NO;
+						return nil;
+					}
+					
+					return result;
+				}
+				reverseBlock:^id(NSUUID *uuid, BOOL *success, NSError **error) {
+					if (uuid == nil) return nil;
+					
+					if (![uuid isKindOfClass:NSUUID.class]) {
+						if (error != NULL) {
+							NSDictionary *userInfo = @{NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert UUID to string", @""),
+													   NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSUUID, got: %@.", @""), uuid],
+													   MTLTransformerErrorHandlingInputValueErrorKey : uuid};
+							*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+						}
+						*success = NO;
+						return nil;
+					}
+					
+					return uuid.UUIDString;
+				}];
+		
+		[NSValueTransformer setValueTransformer:UUIDValueTransformer forName:MTLUUIDValueTransformerName];
+		
 		MTLValueTransformer *booleanValueTransformer = [MTLValueTransformer
-			reversibleTransformerWithBlock:^ id (NSNumber *boolean) {
-				if (![boolean isKindOfClass:NSNumber.class]) return nil;
+			transformerUsingReversibleBlock:^ id (NSNumber *boolean, BOOL *success, NSError **error) {
+				if (boolean == nil) return nil;
+
+				if (![boolean isKindOfClass:NSNumber.class]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: NSLocalizedString(@"Could not convert number to boolean-backed number or vice-versa", @""),
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSNumber, got: %@.", @""), boolean],
+							MTLTransformerErrorHandlingInputValueErrorKey : boolean
+						};
+
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
 				return (NSNumber *)(boolean.boolValue ? kCFBooleanTrue : kCFBooleanFalse);
 			}];
 
@@ -44,98 +157,291 @@ NSString * const MTLBooleanValueTransformerName = @"MTLBooleanValueTransformerNa
 
 #pragma mark Customizable Transformers
 
-+ (NSValueTransformer *)mtl_JSONDictionaryTransformerWithModelClass:(Class)modelClass {
-	NSParameterAssert([modelClass isSubclassOfClass:MTLModel.class]);
-	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)]);
-
-	return [MTLValueTransformer
-		reversibleTransformerWithForwardBlock:^ id (id JSONDictionary) {
-			if (JSONDictionary == nil) return nil;
-
-			NSAssert([JSONDictionary isKindOfClass:NSDictionary.class], @"Expected a dictionary, got: %@", JSONDictionary);
-
-			return [MTLJSONAdapter modelOfClass:modelClass fromJSONDictionary:JSONDictionary error:NULL];
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_arrayMappingTransformerWithTransformer:(NSValueTransformer *)transformer {
+	NSParameterAssert(transformer != nil);
+	
+	id (^forwardBlock)(NSArray *values, BOOL *success, NSError **error) = ^ id (NSArray *values, BOOL *success, NSError **error) {
+		if (values == nil) return nil;
+		
+		if (![values isKindOfClass:NSArray.class]) {
+			if (error != NULL) {
+				NSDictionary *userInfo = @{
+					NSLocalizedDescriptionKey: NSLocalizedString(@"Could not transform non-array type", @""),
+					NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSArray, got: %@.", @""), values],
+					MTLTransformerErrorHandlingInputValueErrorKey: values
+				};
+				
+				*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+			}
+			*success = NO;
+			return nil;
 		}
-		reverseBlock:^ id (id model) {
-			if (model == nil) return nil;
+		
+		NSMutableArray *transformedValues = [NSMutableArray arrayWithCapacity:values.count];
+		NSInteger index = -1;
+		for (id value in values) {
+			index++;
+			if (value == NSNull.null) {
+				[transformedValues addObject:NSNull.null];
+				continue;
+			}
+			
+			id transformedValue = nil;
+			if ([transformer conformsToProtocol:@protocol(MTLTransformerErrorHandling)]) {
+				NSError *underlyingError = nil;
+				transformedValue = [(id<MTLTransformerErrorHandling>)transformer transformedValue:value success:success error:&underlyingError];
+				
+				if (*success == NO) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: NSLocalizedString(@"Could not transform array", @""),
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Could not transform value at index %d", @""), index],
+							NSUnderlyingErrorKey: underlyingError,
+							MTLTransformerErrorHandlingInputValueErrorKey: values
+						};
 
-			NSAssert([model isKindOfClass:MTLModel.class], @"Expected a MTLModel object, got %@", model);
-			NSAssert([model conformsToProtocol:@protocol(MTLJSONSerializing)], @"Expected a model object conforming to <MTLJSONSerializing>, got %@", model);
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					return nil;
+				}
+			} else {
+				transformedValue = [transformer transformedValue:value];
+			}
+			
+			if (transformedValue == nil) continue;
+			
+			[transformedValues addObject:transformedValue];
+		}
+		
+		return transformedValues;
+	};
+	
+	id (^reverseBlock)(NSArray *values, BOOL *success, NSError **error) = nil;
+	if (transformer.class.allowsReverseTransformation) {
+		reverseBlock = ^ id (NSArray *values, BOOL *success, NSError **error) {
+			if (values == nil) return nil;
+			
+			if (![values isKindOfClass:NSArray.class]) {
+				if (error != NULL) {
+					NSDictionary *userInfo = @{
+						NSLocalizedDescriptionKey: NSLocalizedString(@"Could not transform non-array type", @""),
+						NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSArray, got: %@.", @""), values],
+						MTLTransformerErrorHandlingInputValueErrorKey: values
+					};
 
-			return [MTLJSONAdapter JSONDictionaryFromModel:model];
-		}];
-}
+					*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+				}
+				*success = NO;
+				return nil;
+			}
+			
+			NSMutableArray *transformedValues = [NSMutableArray arrayWithCapacity:values.count];
+			NSInteger index = -1;
+			for (id value in values) {
+				index++;
+				if (value == NSNull.null) {
+					[transformedValues addObject:NSNull.null];
 
-+ (NSValueTransformer *)mtl_JSONArrayTransformerWithModelClass:(Class)modelClass {
-	NSValueTransformer *dictionaryTransformer = [self mtl_JSONDictionaryTransformerWithModelClass:modelClass];
-
-	return [MTLValueTransformer
-		reversibleTransformerWithForwardBlock:^ id (NSArray *dictionaries) {
-			if (dictionaries == nil) return nil;
-
-			NSAssert([dictionaries isKindOfClass:NSArray.class], @"Expected an array of dictionaries, got: %@", dictionaries);
-
-			NSMutableArray *models = [NSMutableArray arrayWithCapacity:dictionaries.count];
-			for (id JSONDictionary in dictionaries) {
-				if (JSONDictionary == NSNull.null) {
-					[models addObject:NSNull.null];
 					continue;
 				}
-
-				NSAssert([JSONDictionary isKindOfClass:NSDictionary.class], @"Expected a dictionary or an NSNull, got: %@", JSONDictionary);
-
-				id model = [dictionaryTransformer transformedValue:JSONDictionary];
-				if (model == nil) continue;
-
-				[models addObject:model];
-			}
-
-			return models;
-		}
-		reverseBlock:^ id (NSArray *models) {
-			if (models == nil) return nil;
-
-			NSAssert([models isKindOfClass:NSArray.class], @"Expected an array of MTLModels, got: %@", models);
-
-			NSMutableArray *dictionaries = [NSMutableArray arrayWithCapacity:models.count];
-			for (id model in models) {
-				if (model == NSNull.null) {
-					[dictionaries addObject:NSNull.null];
-					continue;
+				
+				id transformedValue = nil;
+				if ([transformer respondsToSelector:@selector(reverseTransformedValue:success:error:)]) {
+					NSError *underlyingError = nil;
+					transformedValue = [(id<MTLTransformerErrorHandling>)transformer reverseTransformedValue:value success:success error:&underlyingError];
+					
+					if (*success == NO) {
+						if (error != NULL) {
+							NSDictionary *userInfo = @{
+								NSLocalizedDescriptionKey: NSLocalizedString(@"Could not transform array", @""),
+								NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Could not transform value at index %d", @""), index],
+								NSUnderlyingErrorKey: underlyingError,
+								MTLTransformerErrorHandlingInputValueErrorKey: values
+							};
+							
+							*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+						}
+						return nil;
+					}
+				} else {
+					transformedValue = [transformer reverseTransformedValue:value];
 				}
-
-				NSAssert([model isKindOfClass:MTLModel.class], @"Expected an MTLModel or an NSNull, got: %@", model);
-
-				NSDictionary *dict = [dictionaryTransformer reverseTransformedValue:model];
-				if (dict == nil) continue;
-
-				[dictionaries addObject:dict];
+				
+				if (transformedValue == nil) continue;
+				
+				[transformedValues addObject:transformedValue];
 			}
-
-			return dictionaries;
-		}];
+			
+			return transformedValues;
+		};
+	}
+	if (reverseBlock != nil) {
+		return [MTLValueTransformer transformerUsingForwardBlock:forwardBlock reverseBlock:reverseBlock];
+	} else {
+		return [MTLValueTransformer transformerUsingForwardBlock:forwardBlock];
+	}
 }
 
-+ (NSValueTransformer *)mtl_valueMappingTransformerWithDictionary:(NSDictionary *)dictionary {
-	return [self mtl_valueMappingTransformerWithDictionary:dictionary defaultValue:nil reverseDefaultValue:nil];
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_validatingTransformerForClass:(Class)modelClass {
+	NSParameterAssert(modelClass != nil);
+
+	return [MTLValueTransformer transformerUsingForwardBlock:^ id (id value, BOOL *success, NSError **error) {
+		if (value != nil && ![value isKindOfClass:modelClass]) {
+			if (error != NULL) {
+				NSDictionary *userInfo = @{
+					NSLocalizedDescriptionKey: NSLocalizedString(@"Value did not match expected type", @""),
+					NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected %1$@ to be of class %2$@ but got %3$@", @""), value, modelClass, [value class]],
+					MTLTransformerErrorHandlingInputValueErrorKey : value
+				};
+
+				*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+			}
+			*success = NO;
+			return nil;
+		}
+
+		return value;
+	}];
 }
 
 + (NSValueTransformer *)mtl_valueMappingTransformerWithDictionary:(NSDictionary *)dictionary defaultValue:(id)defaultValue reverseDefaultValue:(id)reverseDefaultValue {
 	NSParameterAssert(dictionary != nil);
 	NSParameterAssert(dictionary.count == [[NSSet setWithArray:dictionary.allValues] count]);
 
-	return [MTLValueTransformer reversibleTransformerWithForwardBlock:^(id<NSCopying> key) {
-		return dictionary[key ?: NSNull.null] ?: defaultValue;
-	} reverseBlock:^(id object) {
-		__block id result = nil;
-		[dictionary enumerateKeysAndObjectsUsingBlock:^(id key, id anObject, BOOL *stop) {
-			if ([object isEqual:anObject]) {
-				result = key;
-				*stop = YES;
+	return [MTLValueTransformer
+			transformerUsingForwardBlock:^ id (id <NSCopying> key, BOOL *success, NSError **error) {
+				return dictionary[key ?: NSNull.null] ?: defaultValue;
 			}
-		}];
-		return result ?: reverseDefaultValue;
-	}];
+			reverseBlock:^ id (id value, BOOL *success, NSError **error) {
+				__block id result = nil;
+				[dictionary enumerateKeysAndObjectsUsingBlock:^(id key, id anObject, BOOL *stop) {
+					if ([value isEqual:anObject]) {
+						result = key;
+						*stop = YES;
+					}
+				}];
+
+				return result ?: reverseDefaultValue;
+			}];
 }
 
++ (NSValueTransformer *)mtl_valueMappingTransformerWithDictionary:(NSDictionary *)dictionary {
+	return [self mtl_valueMappingTransformerWithDictionary:dictionary defaultValue:nil reverseDefaultValue:nil];
+}
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_dateTransformerWithDateFormat:(NSString *)dateFormat calendar:(NSCalendar *)calendar locale:(NSLocale *)locale timeZone:(NSTimeZone *)timeZone defaultDate:(NSDate *)defaultDate {
+	NSParameterAssert(dateFormat.length);
+
+	NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
+	dateFormatter.dateFormat = dateFormat;
+	dateFormatter.calendar = calendar;
+	dateFormatter.locale = locale;
+	dateFormatter.timeZone = timeZone;
+	dateFormatter.defaultDate = defaultDate;
+
+	return [NSValueTransformer mtl_transformerWithFormatter:dateFormatter forObjectClass:NSDate.class];
+}
+
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_dateTransformerWithDateFormat:(NSString *)dateFormat locale:(NSLocale *)locale {
+	return [self mtl_dateTransformerWithDateFormat:dateFormat calendar:nil locale:locale timeZone:nil defaultDate:nil];
+}
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_numberTransformerWithNumberStyle:(NSNumberFormatterStyle)numberStyle locale:(NSLocale *)locale {
+	NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
+	numberFormatter.numberStyle = numberStyle;
+	numberFormatter.locale = locale;
+
+	return [self mtl_transformerWithFormatter:numberFormatter forObjectClass:NSNumber.class];
+}
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_transformerWithFormatter:(NSFormatter *)formatter forObjectClass:(Class)objectClass {
+	NSParameterAssert(formatter != nil);
+	NSParameterAssert(objectClass != nil);
+	return [MTLValueTransformer
+			transformerUsingForwardBlock:^ id (NSString *str, BOOL *success, NSError *__autoreleasing *error) {
+				if (str == nil) return nil;
+
+				if (![str isKindOfClass:NSString.class]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+						    NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedString(@"Could not convert string to %@", @""), objectClass],
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an NSString as input, got: %@.", @""), str],
+							MTLTransformerErrorHandlingInputValueErrorKey : str
+						};
+						
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+
+				id object = nil;
+				NSString *errorDescription = nil;
+				*success = [formatter getObjectValue:&object forString:str errorDescription:&errorDescription];
+
+				if (errorDescription != nil) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedString(@"Could not convert string to %@", @""), objectClass],
+							NSLocalizedFailureReasonErrorKey: errorDescription,
+							MTLTransformerErrorHandlingInputValueErrorKey : str
+						};
+						
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+
+				if (![object isKindOfClass:objectClass]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+							NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedString(@"Could not convert string to %@", @""), objectClass],
+							NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an %@ as output from the formatter, got: %@.", @""), objectClass, object],
+						};
+
+						*error = [NSError errorWithDomain:NSCocoaErrorDomain code:NSFormattingError userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+
+				return object;
+			} reverseBlock:^id(id object, BOOL *success, NSError *__autoreleasing *error) {
+				if (object == nil) return nil;
+
+				if (![object isKindOfClass:objectClass]) {
+					if (error != NULL) {
+						NSDictionary *userInfo = @{
+						   NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedString(@"Could not convert %@ to string", @""), objectClass],
+						   NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedString(@"Expected an %@ as input, got: %@.", @""), objectClass, object],
+						   MTLTransformerErrorHandlingInputValueErrorKey : object
+						};
+
+						*error = [NSError errorWithDomain:MTLTransformerErrorHandlingErrorDomain code:MTLTransformerErrorHandlingErrorInvalidInput userInfo:userInfo];
+					}
+					*success = NO;
+					return nil;
+				}
+
+				NSString *string = [formatter stringForObjectValue:object];
+				*success = (string != nil);
+				return string;
+			}];
+}
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-implementations"
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_JSONDictionaryTransformerWithModelClass:(Class)modelClass {
+	return [MTLJSONAdapter dictionaryTransformerWithModelClass:modelClass];
+}
+
++ (NSValueTransformer<MTLTransformerErrorHandling> *)mtl_JSONArrayTransformerWithModelClass:(Class)modelClass {
+	return [MTLJSONAdapter arrayTransformerWithModelClass:modelClass];
+}
+
+#pragma clang diagnostic pop
+
 @end

Mantle/extobjc/EXTKeyPathCoding.h

@@ -50,10 +50,10 @@ NSString *lowercaseStringPath = @keypath(NSString.new, lowercaseString);
  *
  * @code
  
- NSString *employessFirstNamePath = @collectionKeypath(department.employees, Employee.new, firstName)
+ NSString *employeesFirstNamePath = @collectionKeypath(department.employees, Employee.new, firstName)
  // => @"employees.firstName"
  
- NSString *employessFirstNamePath = @collectionKeypath(Department.new, employees, Employee.new, firstName)
+ NSString *employeesFirstNamePath = @collectionKeypath(Department.new, employees, Employee.new, firstName)
  // => @"employees.firstName"
 
  * @endcode

Mantle/extobjc/EXTRuntimeExtensions.m

@@ -7,7 +7,7 @@
 //  Released under the MIT license.
 //
 
-#import "MTLEXTRuntimeExtensions.h"
+#import "EXTRuntimeExtensions.h"
 
 #import <Foundation/Foundation.h>
 

Mantle/extobjc/EXTScope.h

@@ -88,7 +88,7 @@
     _Pragma("clang diagnostic pop")
 
 /*** implementation details follow ***/
-typedef void (^mtl_cleanupBlock_t)();
+typedef void (^mtl_cleanupBlock_t)(void);
 
 void mtl_executeCleanupBlock (__strong mtl_cleanupBlock_t *block);
 

Mantle/extobjc/EXTScope.m

@@ -7,7 +7,7 @@
 //  Released under the MIT license.
 //
 
-#import "MTLEXTScope.h"
+#import "EXTScope.h"
 
 void mtl_executeCleanupBlock (__strong mtl_cleanupBlock_t *block) {
     (*block)();

MantleTests/Info.plist

@@ -7,7 +7,7 @@
 	<key>CFBundleExecutable</key>
 	<string>$(EXECUTABLE_NAME)</string>
 	<key>CFBundleIdentifier</key>
-	<string>org.mantle.$(PRODUCT_NAME:rfc1034identifier)</string>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
 	<key>CFBundleInfoDictionaryVersion</key>
 	<string>6.0</string>
 	<key>CFBundleName</key>

MantleTests/MTLCoreDataObjects.h

@@ -1,52 +0,0 @@
-//
-//  MTLCoreDataObjects.h
-//  Mantle
-//
-//  Created by Robert Böhnke on 9/4/13.
-//  Copyright (c) 2013 GitHub. All rights reserved.
-//
-
-#import <CoreData/CoreData.h>
-
-@class MTLParent;
-
-@interface MTLChild : NSManagedObject
-
-+ (instancetype)insertInManagedObjectContext:(NSManagedObjectContext*)moc;
-
-@property (readwrite, nonatomic, strong) NSNumber *childID;
-
-@property (readwrite, nonatomic, strong) MTLParent *parent1;
-@property (readwrite, nonatomic, strong) MTLParent *parent2;
-
-@end
-
-@interface MTLParent : NSManagedObject
-
-+ (instancetype)insertInManagedObjectContext:(NSManagedObjectContext*)moc;
-
-@property (readwrite, nonatomic, strong) NSDate *date;
-@property (readwrite, nonatomic, strong) NSNumber* number;
-@property (readwrite, nonatomic, copy) NSString *string;
-
-@property (readwrite, nonatomic, copy) NSOrderedSet *orderedChildren;
-@property (readwrite, nonatomic, copy) NSSet *unorderedChildren;
-
-@end
-
-
-@interface MTLParent (CoreDataGeneratedAccesssors)
-
-- (void)addOrderedChildren:(NSOrderedSet*)orderedChildren;
-- (void)removeOrderedChildren:(NSOrderedSet*)orderedChildren;
-
-- (void)addOrderedChildrenObject:(MTLChild*)child;
-- (void)removeOrderedChildrenObject:(MTLChild*)child;
-
-- (void)addUnorderedChildren:(NSSet*)unorderedChildren;
-- (void)removeUnorderedChildren:(NSSet*)unorderedChildren;
-
-- (void)addUnorderedChildrenObject:(MTLChild*)child;
-- (void)removeUnorderedChildrenObject:(MTLChild*)child;
-
-@end

MantleTests/MTLCoreDataObjects.m

@@ -1,56 +0,0 @@
-//
-//  MTLCoreDataObjects.m
-//  Mantle
-//
-//  Created by Robert Böhnke on 9/4/13.
-//  Copyright (c) 2013 GitHub. All rights reserved.
-//
-
-#import "MTLCoreDataObjects.h"
-
-@implementation MTLChild
-
-@dynamic childID;
-@dynamic parent1;
-@dynamic parent2;
-
-+ (id)insertInManagedObjectContext:(NSManagedObjectContext*)moc {
-	NSParameterAssert(moc != nil);
-
-	return [NSEntityDescription insertNewObjectForEntityForName:@"Child" inManagedObjectContext:moc];
-}
-
-@end
-
-@implementation MTLParent
-
-@dynamic date;
-@dynamic number;
-@dynamic string;
-@dynamic unorderedChildren;
-@dynamic orderedChildren;
-
-+ (id)insertInManagedObjectContext:(NSManagedObjectContext*)moc {
-	NSParameterAssert(moc != nil);
-
-	return [NSEntityDescription insertNewObjectForEntityForName:@"Parent" inManagedObjectContext:moc];
-}
-
-// Working around http://openradar.appspot.com/10114310
-- (void)addOrderedChildrenObject:(MTLChild*)child {
-	NSMutableOrderedSet *mutableCopy = [self.orderedChildren mutableCopy];
-
-	[mutableCopy addObject:child];
-
-	self.orderedChildren = [mutableCopy copy];
-}
-
-- (void)removeOrderedChildrenObject:(MTLChild*)child {
-	NSMutableOrderedSet *mutableCopy = [self.orderedChildren mutableCopy];
-
-	[mutableCopy removeObject:child];
-
-	self.orderedChildren = [mutableCopy copy];
-}
-
-@end

MantleTests/MTLCoreDataTestModels.h

@@ -1,64 +0,0 @@
-//
-//  MTLCoreDataTestModels.h
-//  Mantle
-//
-//  Created by Justin Spahr-Summers on 2013-04-05.
-//  Copyright (c) 2013 GitHub. All rights reserved.
-//
-
-#import <Mantle/Mantle.h>
-#import <CoreData/CoreData.h>
-
-// Corresponds to the `Parent` entity.
-@interface MTLParentTestModel : MTLModel <MTLManagedObjectSerializing>
-
-// Associated with the `number` attribute.
-@property (nonatomic, copy) NSString *numberString;
-
-@property (nonatomic, copy) NSDate *date;
-@property (nonatomic, copy) NSString *requiredString;
-
-@property (nonatomic, copy) NSArray *orderedChildren;
-@property (nonatomic, copy) NSSet *unorderedChildren;
-
-@end
-
-// Model for Parent that has custom merging behaviour for CoreData
-@interface MTLParentMergingTestModel : MTLParentTestModel
-
-@end
-
-// Model for Parent entity which doesn't serialize required properties
-@interface MTLParentIncorrectTestModel : MTLModel <MTLManagedObjectSerializing>
-
-@end
-
-// Corresponds to the `Child` entity.
-@interface MTLChildTestModel : MTLModel <MTLManagedObjectSerializing>
-
-// Associated with the `id` attribute.
-@property (nonatomic, assign) NSUInteger childID;
-
-@property (nonatomic, weak) MTLParentTestModel *parent1;
-@property (nonatomic, weak) MTLParentTestModel *parent2;
-
-@end
-
-@interface MTLBadChildTestModel : MTLModel <MTLManagedObjectSerializing>
-
-@property (nonatomic, assign) NSUInteger childID;
-
-@end
-
-// Claims to correspond to the `Empty` entity which lacks the `notSupported`
-// property.
-@interface MTLFailureModel : MTLModel <MTLManagedObjectSerializing>
-
-// Not present in the `Empty` entity.
-@property (nonatomic, assign) NSString *notSupported;
-
-@end
-
-// Maps a non-existant property "name" to the "string" attribute.
-@interface MTLIllegalManagedObjectMappingModel : MTLModel <MTLManagedObjectSerializing>
-@end

MantleTests/MTLCoreDataTestModels.m

@@ -1,154 +0,0 @@
-//
-//  MTLCoreDataTestModels.m
-//  Mantle
-//
-//  Created by Justin Spahr-Summers on 2013-04-05.
-//  Copyright (c) 2013 GitHub. All rights reserved.
-//
-
-#import "MTLCoreDataTestModels.h"
-
-@implementation MTLParentTestModel
-
-+ (NSString *)managedObjectEntityName {
-	return @"Parent";
-}
-
-+ (NSDictionary *)managedObjectKeysByPropertyKey {
-	return @{
-		@"numberString": @"number",
-		@"requiredString": @"string"
-	};
-}
-
-+ (NSSet *)propertyKeysForManagedObjectUniquing {
-	return [NSSet setWithObject:@"numberString"];
-}
-
-+ (NSValueTransformer *)numberStringEntityAttributeTransformer {
-	return [MTLValueTransformer reversibleTransformerWithForwardBlock:^(NSString *str) {
-		return [NSDecimalNumber decimalNumberWithString:str];
-	} reverseBlock:^(NSNumber *num) {
-		return num.stringValue;
-	}];
-}
-
-+ (NSDictionary *)relationshipModelClassesByPropertyKey {
-	return @{
-		@"orderedChildren": MTLChildTestModel.class,
-		@"unorderedChildren": MTLChildTestModel.class,
-	};
-}
-
-- (NSString *)description {
-	return [NSString stringWithFormat:@"<%@: %p>", self.class, self];
-}
-
-@end
-
-@implementation MTLParentMergingTestModel
-
-- (void)mergeValueForKey:(NSString *)key fromManagedObject:(NSManagedObject *)managedObject {
-	if ([key isEqualToString:@"requiredString"]) {
-		self.requiredString = @"merged";
-	}
-}
-
-@end
-
-@implementation MTLParentIncorrectTestModel
-
-+ (NSString *)managedObjectEntityName {
-	return @"Parent";
-}
-
-+ (NSDictionary *)managedObjectKeysByPropertyKey {
-	return @{};
-}
-
-- (NSString *)description {
-	return [NSString stringWithFormat:@"<%@: %p>", self.class, self];
-}
-
-@end
-
-@implementation MTLChildTestModel
-
-+ (NSString *)managedObjectEntityName {
-	return @"Child";
-}
-
-+ (NSDictionary *)managedObjectKeysByPropertyKey {
-	return @{};
-}
-
-+ (NSSet *)propertyKeysForManagedObjectUniquing {
-	return [NSSet setWithObjects:@"childID", nil];
-}
-
-+ (NSDictionary *)relationshipModelClassesByPropertyKey {
-	return @{
-		@"parent1": MTLParentTestModel.class,
-		@"parent2": MTLParentTestModel.class,
-	};
-}
-
-- (NSString *)description {
-	return [NSString stringWithFormat:@"<%@: %p>", self.class, self];
-}
-
-@end
-
-@implementation MTLBadChildTestModel
-
-+ (NSString *)managedObjectEntityName {
-	return @"BadChild";
-}
-
-+ (NSDictionary *)managedObjectKeysByPropertyKey {
-	return @{};
-}
-
-+ (NSSet *)propertyKeysForManagedObjectUniquing {
-	return [NSSet setWithObjects:@"childID", nil];
-}
-
-- (NSString *)description {
-	return [NSString stringWithFormat:@"<%@: %p>", self.class, self];
-}
-
-@end
-
-@implementation MTLFailureModel
-
-+ (NSDictionary *)managedObjectKeysByPropertyKey {
-	return @{};
-}
-
-+ (NSString *)managedObjectEntityName {
-	return @"Empty";
-}
-
-- (NSString *)description {
-	return [NSString stringWithFormat:@"<%@: %p>", self.class, self];
-}
-
-@end
-
-@implementation MTLIllegalManagedObjectMappingModel
-
-+ (NSString *)managedObjectEntityName {
-	return @"Parent";
-}
-
-+ (NSDictionary *)managedObjectKeysByPropertyKey {
-	return @{
-		@"name": @"username"
-	};
-}
-
-- (NSString *)description {
-	return [NSString stringWithFormat:@"<%@: %p>", self.class, self];
-}
-
-@end

MantleTests/MTLDictionaryManipulationSpec.m

@@ -38,27 +38,27 @@ describe(@"-mtl_dictionaryByAddingEntriesFromDictionary:", ^{
 	});
 });
 
-describe(@"-mtl_dictionaryByRemovingEntriesWithKeys:", ^{
+describe(@"-mtl_dictionaryByRemovingValuesForKeys:", ^{
 	NSDictionary *dict = @{ @"foo": @"bar", @(5): NSNull.null };
 
 	it(@"should return the same dictionary when removing keys that don't exist in the receiver", ^{
-		NSDictionary *removed = [dict mtl_dictionaryByRemovingEntriesWithKeys:[NSSet setWithObject:@"hi"]];
+		NSDictionary *removed = [dict mtl_dictionaryByRemovingValuesForKeys:@[ @"hi"]];
 		expect(removed).to(equal(dict));
 	});
 
 	it(@"should return the same dictionary when given a nil array of keys", ^{
-		NSDictionary *removed = [dict mtl_dictionaryByRemovingEntriesWithKeys:nil];
+		NSDictionary *removed = [dict mtl_dictionaryByRemovingValuesForKeys:nil];
 		expect(removed).to(equal(dict));
 	});
 
 	it(@"should remove all the entries for the given keys", ^{
-		NSDictionary *removed = [dict mtl_dictionaryByRemovingEntriesWithKeys:[NSSet setWithObject:@(5)]];
+		NSDictionary *removed = [dict mtl_dictionaryByRemovingValuesForKeys:@[ @5 ]];
 		NSDictionary *expected = @{ @"foo": @"bar" };
 		expect(removed).to(equal(expected));
 	});
 
 	it(@"should return an empty dictionary when it removes all its keys", ^{
-		NSDictionary *removed = [dict mtl_dictionaryByRemovingEntriesWithKeys:[NSSet setWithArray:dict.allKeys]];
+		NSDictionary *removed = [dict mtl_dictionaryByRemovingValuesForKeys:dict.allKeys];
 		NSDictionary *expected = @{};
 		expect(removed).to(equal(expected));
 	});

MantleTests/MTLDictionaryMappingSpec.m

@@ -0,0 +1,28 @@
+//
+//  MTLDictionaryMappingSpec.m
+//  Mantle
+//
+//  Created by Robert Böhnke on 10/23/13.
+//  Copyright (c) 2013 GitHub. All rights reserved.
+//
+
+#import <Quick/Quick.h>
+#import <Nimble/Nimble.h>
+#import "MTLTestModel.h"
+
+#import "NSDictionary+MTLMappingAdditions.h"
+
+QuickSpecBegin(MTLDictionaryMappingAdditions)
+
+it(@"should return a mapping", ^{
+	NSDictionary *mapping = @{
+		@"name": @"name",
+		@"count": @"count",
+		@"nestedName": @"nestedName",
+		@"weakModel": @"weakModel"
+	};
+
+	expect([NSDictionary mtl_identityPropertyMapWithModel:MTLTestModel.class]).to(equal(mapping));
+});
+
+QuickSpecEnd

MantleTests/MTLJSONAdapterSpec.m

@@ -10,29 +10,40 @@
 #import <Nimble/Nimble.h>
 #import <Quick/Quick.h>
 
+#import "MTLTestJSONAdapter.h"
 #import "MTLTestModel.h"
+#import "MTLTransformerErrorExamples.h"
 
 @interface MTLJSONAdapter (SpecExtensions)
 
 // Used for testing transformer lifetimes.
-- (NSValueTransformer *)JSONTransformerForKey:(NSString *)key;
++ (NSValueTransformer *)NSDateJSONTransformer;
+
+@end
+
+@implementation MTLJSONAdapter (SpecExtensions)
+
++ (NSValueTransformer *)NSDateJSONTransformer {
+	return [[NSValueTransformer alloc] init];
+}
 
 @end
 
 QuickSpecBegin(MTLJSONAdapterSpec)
 
-it(@"should initialize from JSON", ^{
+it(@"should initialize with a model class", ^{
 	NSDictionary *values = @{
 		@"username": NSNull.null,
 		@"count": @"5",
 	};
 
-	NSError *error = nil;
-	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithJSONDictionary:values modelClass:MTLTestModel.class error:&error];
+	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithModelClass:MTLTestModel.class];
 	expect(adapter).notTo(beNil());
+
+	NSError *error = nil;
+	MTLTestModel *model = [adapter modelFromJSONDictionary:values error:&error];
 	expect(error).to(beNil());
 
-	MTLTestModel *model = (id)adapter.model;
 	expect(model).notTo(beNil());
 	expect(model.name).to(beNil());
 	expect(@(model.count)).to(equal(@5));
@@ -43,26 +54,9 @@ it(@"should initialize from JSON", ^{
 		@"nested": @{ @"name": NSNull.null },
 	};
 
-	expect(adapter.JSONDictionary).to(equal(JSONDictionary));
-});
-
-it(@"should initialize from a model", ^{
-	MTLTestModel *model = [MTLTestModel modelWithDictionary:@{
-		@"name": @"foobar",
-		@"count": @5,
-	} error:NULL];
-
-	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithModel:model];
-	expect(adapter).notTo(beNil());
-	expect(adapter.model).to(beIdenticalTo(model));
-
-	NSDictionary *JSONDictionary = @{
-		@"username": @"foobar",
-		@"count": @"5",
-		@"nested": @{ @"name": NSNull.null },
-	};
-
-	expect(adapter.JSONDictionary).to(equal(JSONDictionary));
+	__block NSError *serializationError;
+	expect([adapter JSONDictionaryFromModel:model error:&serializationError]).to(equal(JSONDictionary));
+	expect(serializationError).to(beNil());
 });
 
 it(@"should initialize nested key paths from JSON", ^{
@@ -81,7 +75,35 @@ it(@"should initialize nested key paths from JSON", ^{
 	expect(@(model.count)).to(equal(@0));
 	expect(model.nestedName).to(equal(@"bar"));
 
-	expect([MTLJSONAdapter JSONDictionaryFromModel:model]).to(equal(values));
+	__block NSError *serializationError;
+	expect([MTLJSONAdapter JSONDictionaryFromModel:model error:&serializationError]).to(equal(values));
+	expect(serializationError).to(beNil());
+});
+
+it(@"it should initialize properties with multiple key paths from JSON", ^{
+	NSDictionary *values = @{
+		@"location": @20,
+		@"length": @12,
+		@"nested": @{
+			@"location": @12,
+			@"length": @34
+		}
+	};
+
+	NSError *error = nil;
+	MTLMultiKeypathModel *model = [MTLJSONAdapter modelOfClass:MTLMultiKeypathModel.class fromJSONDictionary:values error:&error];
+	expect(model).notTo(beNil());
+	expect(error).to(beNil());
+
+	expect(@(model.range.location)).to(equal(@20));
+	expect(@(model.range.length)).to(equal(@12));
+
+	expect(@(model.nestedRange.location)).to(equal(@12));
+	expect(@(model.nestedRange.length)).to(equal(@34));
+
+	__block NSError *serializationError;
+	expect([MTLJSONAdapter JSONDictionaryFromModel:model error:&serializationError]).to(equal(values));
+	expect(serializationError).to(beNil());
 });
 
 it(@"should return nil and error with an invalid key path from JSON",^{
@@ -116,10 +138,11 @@ it(@"should support key paths across arrays", ^{
 
 	NSError *error = nil;
 	MTLArrayTestModel *model = [MTLJSONAdapter modelOfClass:MTLArrayTestModel.class fromJSONDictionary:values error:&error];
-	expect(model).notTo(beNil());
-	expect(error).to(beNil());
+	expect(model).to(beNil());
+	expect(error).notTo(beNil());
 
-	expect(model.names).to(equal((@[ @"foo", @"bar", @"baz" ])));
+	expect(error.domain).to(equal(MTLJSONAdapterErrorDomain));
+	expect(@(error.code)).to(equal(@(MTLJSONAdapterErrorInvalidJSONDictionary)));
 });
 
 it(@"should initialize without returning any error when using a JSON dictionary which Null.null as value",^{
@@ -139,25 +162,6 @@ it(@"should initialize without returning any error when using a JSON dictionary
 	expect(model.nestedName).to(beNil());
 });
 
-it(@"should return nil and an error with a nil JSON dictionary", ^{
-	NSError *error = nil;
-	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithJSONDictionary:nil modelClass:MTLTestModel.class error:&error];
-	expect(adapter).to(beNil());
-	expect(error).notTo(beNil());
-	expect(error.domain).to(equal(MTLJSONAdapterErrorDomain));
-	expect(@(error.code)).to(equal(@(MTLJSONAdapterErrorInvalidJSONDictionary)));
-});
-
-it(@"should return nil and an error with a wrong data type as dictionary", ^{
-	NSError *error = nil;
-	id wrongDictionary = @"";
-	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithJSONDictionary:wrongDictionary modelClass:MTLTestModel.class error:&error];
-	expect(adapter).to(beNil());
-	expect(error).notTo(beNil());
-	expect(error.domain).to(equal(MTLJSONAdapterErrorDomain));
-	expect(@(error.code)).to(equal(@(MTLJSONAdapterErrorInvalidJSONDictionary)));
-});
-
 it(@"should ignore unrecognized JSON keys", ^{
 	NSDictionary *values = @{
 		@"foobar": @"foo",
@@ -189,6 +193,172 @@ it(@"should fail to initialize if JSON dictionary validation fails", ^{
 	expect(@(error.code)).to(equal(@(MTLTestModelNameTooLong)));
 });
 
+it(@"should implicitly transform NSStrings to URLs", ^{
+	NSDictionary *values = @{
+		@"URL": @"http://github.com/1",
+		@"otherURL": @"http://github.com/2",
+	};
+	
+	NSError *error = nil;
+	MTLURLSubclassModel *model = [MTLJSONAdapter modelOfClass:MTLURLSubclassModel.class fromJSONDictionary:values error:&error];
+	expect(model.URL).to(equal([NSURL URLWithString:@"http://github.com/1"]));
+	expect(model.otherURL).to(equal([NSURL URLWithString:@"http://github.com/2"]));
+	expect(error).to(beNil());
+});
+
+it(@"should implicitly transform URLs", ^{
+	MTLURLModel *model = [[MTLURLModel alloc] init];
+	
+	NSError *error = nil;
+	NSDictionary *JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:model error:&error];
+	
+	expect(JSONDictionary[@"URL"]).to(equal(@"http://github.com"));
+	expect(error).to(beNil());
+});
+
+
+it(@"should implicitly transform NSStrings to UUIDs", ^{
+	NSDictionary *values = @{
+		@"UUID": @"D278C472-6DC3-4EE1-A947-861E6AF311C3",
+		@"otherUUID": @"24E1E56A-3F37-4ECE-8310-931F6ACD401A",
+	};
+	
+	NSError *error = nil;
+	MTLUUIDSubclassModel *model = [MTLJSONAdapter modelOfClass:MTLUUIDSubclassModel.class fromJSONDictionary:values error:&error];
+	expect(model.UUID).to(equal([[NSUUID alloc] initWithUUIDString:@"D278C472-6DC3-4EE1-A947-861E6AF311C3"]));
+	expect(model.otherUUID).to(equal([[NSUUID alloc] initWithUUIDString:@"24E1E56A-3F37-4ECE-8310-931F6ACD401A"]));
+	expect(error).to(beNil());
+});
+
+it(@"should implicitly transform UUIDs", ^{
+	MTLUUIDModel *model = [[MTLUUIDModel alloc] init];
+
+	NSError *error = nil;
+	NSDictionary *JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:model error:&error];
+
+	expect(JSONDictionary[@"UUID"]).to(equal(@"4A275FBD-8217-4397-964B-403F4C2B8545"));
+	expect(error).to(beNil());
+});
+
+it(@"should implicitly transform BOOLs", ^{
+	MTLBoolModel *model = [[MTLBoolModel alloc] init];
+
+	NSError *error = nil;
+	NSDictionary *JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:model error:&error];
+
+	expect(JSONDictionary[@"flag"]).to(beIdenticalTo((id)kCFBooleanFalse));
+	expect(error).to(beNil());
+});
+
+it(@"should not invoke implicit transformers for property keys not actually backed by properties", ^{
+	MTLNonPropertyModel *model = [[MTLNonPropertyModel alloc] init];
+
+	NSError *error = nil;
+	NSDictionary *JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:model error:&error];
+
+	expect(error).to(beNil());
+	expect(JSONDictionary[@"homepage"]).to(equal(model.homepage));
+});
+
+it(@"should fail to initialize if JSON transformer fails", ^{
+	NSDictionary *values = @{
+		@"URL": @666,
+	};
+
+	NSError *error = nil;
+	MTLModel *model = [MTLJSONAdapter modelOfClass:MTLURLModel.class fromJSONDictionary:values error:&error];
+	expect(model).to(beNil());
+	expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+	expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+	expect(error.userInfo[MTLTransformerErrorHandlingInputValueErrorKey]).to(equal(@666));
+});
+
+it(@"should fail to deserialize if the JSON types don't match the primitive properties", ^{
+	NSDictionary *values = @{
+		@"flag": @"Potentially"
+	};
+
+	NSError *error = nil;
+	MTLModel *model = [MTLJSONAdapter modelOfClass:MTLBoolModel.class fromJSONDictionary:values error:&error];
+	expect(model).to(beNil());
+
+	expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+	expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+	expect(error.userInfo[MTLTransformerErrorHandlingInputValueErrorKey]).to(equal(@"Potentially"));
+});
+
+it(@"should fail to deserialize if the JSON types don't match the properties", ^{
+	NSDictionary *values = @{
+		@"string": @666
+	};
+
+	NSError *error = nil;
+	MTLModel *model = [MTLJSONAdapter modelOfClass:MTLStringModel.class fromJSONDictionary:values error:&error];
+	expect(model).to(beNil());
+
+	expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+	expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+	expect(error.userInfo[MTLTransformerErrorHandlingInputValueErrorKey]).to(equal(@666));
+});
+
+it(@"should allow subclasses to filter serialized property keys", ^{
+	NSDictionary *values = @{
+		@"username": @"foo",
+		@"count": @"5",
+		@"nested": @{ @"name": NSNull.null }
+	};
+
+	MTLTestJSONAdapter *adapter = [[MTLTestJSONAdapter alloc] initWithModelClass:MTLTestModel.class];
+
+	NSError *error;
+	MTLTestModel *model = [adapter modelFromJSONDictionary:values error:&error];
+	expect(model).notTo(beNil());
+	expect(error).to(beNil());
+
+	NSDictionary *complete = [adapter JSONDictionaryFromModel:model error:&error];
+	NSDictionary *expected = [values mtl_dictionaryByAddingEntriesFromDictionary:@{ @"test": @YES }];
+
+	expect(complete).to(equal(expected));
+	expect(error).to(beNil());
+
+	adapter.ignoredPropertyKeys = [NSSet setWithObjects:@"count", @"nestedName", nil];
+
+	NSDictionary *partial = [adapter JSONDictionaryFromModel:model error:&error];
+	expected = @{
+		@"username": @"foo",
+		@"test": @YES,
+	};
+
+	expect(partial).to(equal(expected));
+	expect(error).to(beNil());
+});
+
+it(@"should accept any object for id properties", ^{
+	NSDictionary *values = @{
+		@"anyObject": @"Not an NSValue"
+	};
+
+	NSError *error = nil;
+	MTLIDModel *model = [MTLJSONAdapter modelOfClass:MTLIDModel.class fromJSONDictionary:values error:&error];
+	expect(model).notTo(beNil());
+	expect(model.anyObject).to(equal(@"Not an NSValue"));
+
+	expect(error.domain).to(beNil());
+});
+
+it(@"should fail to serialize if a JSON transformer errors", ^{
+	MTLURLModel *model = [[MTLURLModel alloc] init];
+
+	[model setValue:@"totallyNotAnNSURL" forKey:@"URL"];
+
+	NSError *error;
+	NSDictionary *dictionary = [MTLJSONAdapter JSONDictionaryFromModel:model error:&error];
+	expect(dictionary).to(beNil());
+	expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+	expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+	expect(error.userInfo[MTLTransformerErrorHandlingInputValueErrorKey]).to(equal(@"totallyNotAnNSURL"));
+});
+
 it(@"should parse a different model class", ^{
 	NSDictionary *values = @{
 		@"username": @"foo",
@@ -205,7 +375,51 @@ it(@"should parse a different model class", ^{
 	expect(@(model.count)).to(equal(@0));
 	expect(model.nestedName).to(equal(@"bar"));
 
-	expect([MTLJSONAdapter JSONDictionaryFromModel:model]).to(equal(values));
+	__block NSError *serializationError;
+	expect([MTLJSONAdapter JSONDictionaryFromModel:model error:&serializationError]).to(equal(values));
+	expect(serializationError).to(beNil());
+});
+
+it(@"should serialize different model classes", ^{
+	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithModelClass:MTLClassClusterModel.class];
+
+	MTLChocolateClassClusterModel *chocolate = [MTLChocolateClassClusterModel modelWithDictionary:@{
+		@"bitterness": @100
+	} error:NULL];
+
+	NSError *error = nil;
+	NSDictionary *chocolateValues = [adapter JSONDictionaryFromModel:chocolate error:&error];
+
+	expect(error).to(beNil());
+	expect(chocolateValues).to(equal((@{
+		@"flavor": @"chocolate",
+		@"chocolate_bitterness": @"100"
+	})));
+
+	MTLStrawberryClassClusterModel *strawberry = [MTLStrawberryClassClusterModel modelWithDictionary:@{
+		@"freshness": @20
+	} error:NULL];
+
+	NSDictionary *strawberryValues = [adapter JSONDictionaryFromModel:strawberry error:&error];
+
+	expect(error).to(beNil());
+	expect(strawberryValues).to(equal((@{
+		@"flavor": @"strawberry",
+		@"strawberry_freshness": @20
+	})));
+});
+
+it(@"should parse model classes not inheriting from MTLModel", ^{
+	NSDictionary *values = @{
+		@"name": @"foo",
+	};
+
+	NSError *error = nil;
+	MTLConformingModel *model = [MTLJSONAdapter modelOfClass:MTLConformingModel.class fromJSONDictionary:values error:&error];
+	expect(model).to(beAnInstanceOf(MTLConformingModel.class));
+	expect(error).to(beNil());
+
+	expect(model.name).to(equal(@"foo"));
 });
 
 it(@"should return an error when no suitable model class is found", ^{
@@ -218,6 +432,119 @@ it(@"should return an error when no suitable model class is found", ^{
 	expect(@(error.code)).to(equal(@(MTLJSONAdapterErrorNoClassFound)));
 });
 
+it(@"should validate models", ^{
+	NSError *error = nil;
+	MTLValidationModel *model = [MTLJSONAdapter modelOfClass:MTLValidationModel.class fromJSONDictionary:@{} error:&error];
+
+	expect(model).to(beNil());
+
+	expect(error).notTo(beNil());
+	expect(error.domain).to(equal(MTLTestModelErrorDomain));
+	expect(@(error.code)).to(equal(@(MTLTestModelNameMissing)));
+});
+
+describe(@"JSON transformers", ^{
+	describe(@"dictionary transformer", ^{
+		__block NSValueTransformer *transformer;
+		
+		__block MTLTestModel *model;
+		__block NSDictionary *JSONDictionary;
+		
+		beforeEach(^{
+			model = [[MTLTestModel alloc] init];
+			JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:model error:NULL];
+			
+			transformer = [MTLJSONAdapter dictionaryTransformerWithModelClass:MTLTestModel.class];
+			expect(transformer).notTo(beNil());
+		});
+		
+		it(@"should transform a JSON dictionary into a model", ^{
+			expect([transformer transformedValue:JSONDictionary]).to(equal(model));
+		});
+		
+		it(@"should transform a model into a JSON dictionary", ^{
+			expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+			expect([transformer reverseTransformedValue:model]).to(equal(JSONDictionary));
+		});
+		
+		itBehavesLike(MTLTransformerErrorExamples, ^{
+			return @{
+				MTLTransformerErrorExamplesTransformer: transformer,
+				MTLTransformerErrorExamplesInvalidTransformationInput: NSNull.null,
+				MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+			};
+		});
+	});
+	
+	describe(@"external representation array transformer", ^{
+		__block NSValueTransformer *transformer;
+		
+		__block NSArray *models;
+		__block NSArray *JSONDictionaries;
+		
+		beforeEach(^{
+			NSMutableArray *uniqueModels = [NSMutableArray array];
+			NSMutableArray *mutableDictionaries = [NSMutableArray array];
+			
+			for (NSUInteger i = 0; i < 10; i++) {
+				MTLTestModel *model = [[MTLTestModel alloc] init];
+				model.count = i;
+				
+				[uniqueModels addObject:model];
+				
+				NSDictionary *dict = [MTLJSONAdapter JSONDictionaryFromModel:model error:NULL];
+				expect(dict).notTo(beNil());
+				
+				[mutableDictionaries addObject:dict];
+			}
+			
+			uniqueModels[2] = NSNull.null;
+			mutableDictionaries[2] = NSNull.null;
+			
+			models = [uniqueModels copy];
+			JSONDictionaries = [mutableDictionaries copy];
+			
+			transformer = [MTLJSONAdapter arrayTransformerWithModelClass:MTLTestModel.class];
+			expect(transformer).notTo(beNil());
+		});
+		
+		it(@"should transform JSON dictionaries into models", ^{
+			expect([transformer transformedValue:JSONDictionaries]).to(equal(models));
+		});
+		
+		it(@"should transform models into JSON dictionaries", ^{
+			expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+			expect([transformer reverseTransformedValue:models]).to(equal(JSONDictionaries));
+		});
+		
+		itBehavesLike(MTLTransformerErrorExamples, ^{
+			return @{
+				MTLTransformerErrorExamplesTransformer: transformer,
+				MTLTransformerErrorExamplesInvalidTransformationInput: NSNull.null,
+				MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+			};
+		});
+	});
+
+	it(@"should use receiving class for serialization", ^{
+		NSDictionary *values = @{
+			@"username": @"foo",
+			@"count": @"5",
+			@"nested": @{ @"name": NSNull.null }
+		};
+		
+		NSValueTransformer *transformer = [MTLTestJSONAdapter dictionaryTransformerWithModelClass:MTLTestModel.class];
+
+		MTLTestModel *model = [transformer transformedValue:values];
+		expect(model).to(beAKindOf(MTLTestModel.class));
+		expect(model).notTo(beNil());
+
+		NSDictionary *serialized = [transformer reverseTransformedValue:model];
+		expect(serialized).notTo(beNil());
+		expect(serialized[@"test"]).to(beTruthy());
+	});
+});
+
 describe(@"Deserializing multiple models", ^{
 	NSDictionary *value1 = @{
 		@"username": @"foo"
@@ -277,7 +604,10 @@ it(@"should return an array of dictionaries from models", ^{
 	MTLTestModel *model2 = [[MTLTestModel alloc] init];
 	model2.name = @"bar";
 
-	NSArray *JSONArray = [MTLJSONAdapter JSONArrayFromModels:@[ model1, model2 ]];
+	NSError *error;
+	NSArray *JSONArray = [MTLJSONAdapter JSONArrayFromModels:@[ model1, model2 ] error:&error];
+
+	expect(error).to(beNil());
 
 	expect(JSONArray).notTo(beNil());
 	expect(@(JSONArray.count)).to(equal(@2));
@@ -286,13 +616,10 @@ it(@"should return an array of dictionaries from models", ^{
 });
 
 it(@"should not leak transformers", ^{
-	MTLTestModel *model = [[MTLTestModel alloc] init];
-	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithModel:model];
-
 	__weak id weakTransformer;
 
 	@autoreleasepool {
-		id transformer = [adapter JSONTransformerForKey:@"count"];
+		id transformer = [MTLJSONAdapter transformerForModelPropertiesOfClass:NSDate.class];
 		weakTransformer = transformer;
 
 		expect(transformer).notTo(beNil());
@@ -301,4 +628,65 @@ it(@"should not leak transformers", ^{
 	expect(weakTransformer).toEventually(beNil());
 });
 
+it(@"should support recursive models", ^{
+	NSDictionary *dictionary = @{
+		@"owner": @{ @"name": @"Cameron" },
+		@"users": @[
+			@{ @"name": @"Dimitri" },
+			@{ @"name": @"John" },
+		],
+	};
+
+	NSError *error = nil;
+	MTLRecursiveGroupModel *group = [MTLJSONAdapter modelOfClass:MTLRecursiveGroupModel.class fromJSONDictionary:dictionary error:&error];
+	expect(group).notTo(beNil());
+	expect(@(group.users.count)).to(equal(@2));
+});
+
+it(@"should automatically transform a property that conforms to MTLJSONSerializing", ^{
+	NSDictionary *JSONDictionary = @{
+		@"property": @"property",
+		@"conformingMTLJSONSerializingProperty":@{
+			@"username": @"testName",
+			@"count": @"5",
+		},
+		@"nonConformingMTLJSONSerializingProperty": NSNull.null
+	};
+
+	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithModelClass:MTLPropertyDefaultAdapterModel.class];
+	expect(adapter).notTo(beNil());
+
+	NSError *error = nil;
+	MTLPropertyDefaultAdapterModel *model = [MTLJSONAdapter modelOfClass:MTLPropertyDefaultAdapterModel.class fromJSONDictionary:JSONDictionary error:&error];
+	expect(model).notTo(beNil());
+	expect(model.conformingMTLJSONSerializingProperty).notTo(beNil());
+	expect(model.conformingMTLJSONSerializingProperty.name).to(equal(@"testName"));
+	expect(model.nonConformingMTLJSONSerializingProperty).to(beNil());
+	expect(model.property).to(equal(@"property"));
+	expect(error).to(beNil());
+});
+
+it(@"should not automatically transform a property that conforms to MTLModel but not MTLJSONSerializing", ^{
+	NSDictionary *JSONDictionary = @{
+		@"property": @"property",
+		@"conformingMTLJSONSerializingProperty":@{
+			@"username": @"testName",
+			@"count": @"5",
+		},
+		/// Triggers an error since the dictionary is not automatically parsed
+		/// and no transformer is supplied.
+		@"nonConformingMTLJSONSerializingProperty": @{}
+	};
+
+	MTLJSONAdapter *adapter = [[MTLJSONAdapter alloc] initWithModelClass:MTLPropertyDefaultAdapterModel.class];
+	expect(adapter).notTo(beNil());
+
+	NSError *error = nil;
+	MTLPropertyDefaultAdapterModel *model = [adapter modelFromJSONDictionary:JSONDictionary error:&error];
+	expect(model).to(beNil());
+	expect(error).notTo(beNil());
+	expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+	expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+});
+
 QuickSpecEnd

MantleTests/MTLManagedObjectAdapterSpec.m

@@ -1,410 +0,0 @@
-//
-//  MTLManagedObjectAdapterSpec.m
-//  Mantle
-//
-//  Created by Justin Spahr-Summers on 2013-05-17.
-//  Copyright (c) 2013 GitHub. All rights reserved.
-//
-
-#import <Mantle/Mantle.h>
-#import <Nimble/Nimble.h>
-#import <Quick/Quick.h>
-
-#import "MTLCoreDataObjects.h"
-
-#import "MTLCoreDataTestModels.h"
-
-QuickSpecBegin(MTLManagedObjectAdapterSpec)
-
-__block NSPersistentStoreCoordinator *persistentStoreCoordinator;
-
-beforeEach(^{
-	NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:@[ [NSBundle bundleForClass:self.class] ]];
-	expect(model).notTo(beNil());
-
-	persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
-	expect(persistentStoreCoordinator).notTo(beNil());
-	expect([persistentStoreCoordinator addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:NULL]).notTo(beNil());
-});
-
-describe(@"with a confined context", ^{
-	__block NSManagedObjectContext *context;
-
-	__block NSEntityDescription *parentEntity;
-	__block NSEntityDescription *childEntity;
-
-	beforeEach(^{
-		context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
-		expect(context).notTo(beNil());
-
-		context.undoManager = nil;
-		context.persistentStoreCoordinator = persistentStoreCoordinator;
-
-		parentEntity = [NSEntityDescription entityForName:@"Parent" inManagedObjectContext:context];
-		expect(parentEntity).notTo(beNil());
-
-		childEntity = [NSEntityDescription entityForName:@"Child" inManagedObjectContext:context];
-		expect(childEntity).notTo(beNil());
-	});
-
-	describe(@"+modelOfClass:fromManagedObject:error:", ^{
-		__block MTLParent *parent;
-
-		__block NSDate *date;
-		__block NSString *numberString;
-		__block NSString *requiredString;
-
-		beforeEach(^{
-			date = [NSDate date];
-			numberString = @"123";
-			requiredString = @"foobar";
-
-			parent = [MTLParent insertInManagedObjectContext:context];
-			expect(parent).notTo(beNil());
-
-			for (NSUInteger i = 0; i < 3; i++) {
-				MTLChild *child = [MTLChild insertInManagedObjectContext:context];
-				expect(child).notTo(beNil());
-
-				child.childID = @(i);
-				[parent addOrderedChildrenObject:child];
-			}
-
-			for (NSUInteger i = 3; i < 6; i++) {
-				MTLChild *child = [MTLChild insertInManagedObjectContext:context];
-				expect(child).notTo(beNil());
-
-				child.childID = @(i);
-				[parent addUnorderedChildrenObject:child];
-			}
-
-			parent.string = requiredString;
-
-			__block NSError *error = nil;
-			expect(@([context save:&error])).to(beTruthy());
-			expect(error).to(beNil());
-
-			// Make sure that pending changes are picked up too.
-			[parent setValue:@(numberString.integerValue) forKey:@"number"];
-			[parent setValue:date forKey:@"date"];
-		});
-
-		it(@"should initialize a MTLParentTestModel with children", ^{
-			NSError *error = nil;
-			MTLParentTestModel *parentModel = [MTLManagedObjectAdapter modelOfClass:MTLParentTestModel.class fromManagedObject:parent error:&error];
-			expect(parentModel).to(beAnInstanceOf(MTLParentTestModel.class));
-			expect(error).to(beNil());
-
-			expect(parentModel.date).to(equal(date));
-			expect(parentModel.numberString).to(equal(numberString));
-			expect(parentModel.requiredString).to(equal(requiredString));
-
-			expect(@(parentModel.orderedChildren.count)).to(equal(@3));
-			expect(@(parentModel.unorderedChildren.count)).to(equal(@3));
-
-			for (NSUInteger i = 0; i < 3; i++) {
-				MTLChildTestModel *child = parentModel.orderedChildren[i];
-				expect(child).to(beAnInstanceOf(MTLChildTestModel.class));
-
-				expect(@(child.childID)).to(equal(@(i)));
-				expect(child.parent1).to(beNil());
-				expect(child.parent2).to(beIdenticalTo(parentModel));
-			}
-
-			for (MTLChildTestModel *child in parentModel.unorderedChildren) {
-				expect(child).to(beAnInstanceOf(MTLChildTestModel.class));
-
-				expect(@(child.childID)).to(beGreaterThanOrEqualTo(@3));
-				expect(@(child.childID)).to(beLessThan(@6));
-
-				expect(child.parent1).to(beIdenticalTo(parentModel));
-				expect(child.parent2).to(beNil());
-			}
-		});
-	});
-
-	describe(@"+managedObjectFromModel:insertingIntoContext:error:", ^{
-		__block MTLParentTestModel *parentModel;
-
-		beforeEach(^{
-			parentModel = [MTLParentTestModel modelWithDictionary:@{
-				@"date": [NSDate date],
-				@"numberString": @"1234",
-				@"requiredString": @"foobar"
-			} error:NULL];
-			expect(parentModel).notTo(beNil());
-
-			NSMutableArray *orderedChildren = [NSMutableArray array];
-			NSMutableSet *unorderedChildren = [NSMutableSet set];
-
-			for (NSUInteger i = 0; i < 3; i++) {
-				MTLChildTestModel *child = [MTLChildTestModel modelWithDictionary:@{
-					@"childID": @(i),
-					@"parent2": parentModel
-				} error:NULL];
-				expect(child).notTo(beNil());
-
-				[orderedChildren addObject:child];
-			}
-
-			for (NSUInteger i = 3; i < 6; i++) {
-				MTLChildTestModel *child = [MTLChildTestModel modelWithDictionary:@{
-					@"childID": @(i),
-					@"parent1": parentModel
-				} error:NULL];
-				expect(child).notTo(beNil());
-
-				[unorderedChildren addObject:child];
-			}
-
-			parentModel.orderedChildren = orderedChildren;
-			parentModel.unorderedChildren = unorderedChildren;
-		});
-
-		it(@"should insert a managed object with children", ^{
-			__block NSError *error = nil;
-			MTLParent *parent = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&error];
-			expect(parent).notTo(beNil());
-			expect(parent).to(beAnInstanceOf(MTLParent.class));
-			expect(error).to(beNil());
-
-			expect(parent.entity).to(equal(parentEntity));
-			expect(context.insertedObjects).to(contain(parent));
-
-			expect(parent.date).to(equal(parentModel.date));
-			expect(parent.number.stringValue).to(equal(parentModel.numberString));
-			expect(parent.string).to(equal(parentModel.requiredString));
-
-			expect(@(parent.orderedChildren.count)).to(equal(@3));
-			expect(@(parent.unorderedChildren.count)).to(equal(@3));
-
-			for (NSUInteger i = 0; i < 3; i++) {
-				MTLChild *child = parent.orderedChildren[i];
-				expect(child).to(beAnInstanceOf(MTLChild.class));
-
-				expect(child.entity).to(equal(childEntity));
-				expect(context.insertedObjects).to(contain(child));
-
-				expect(child.childID).to(equal(@(i)));
-				expect(child.parent1).to(beNil());
-				expect(child.parent2).to(equal(parent));
-			}
-
-			for (MTLChild *child in parent.unorderedChildren) {
-				expect(child).to(beAnInstanceOf(MTLChild.class));
-
-				expect(child.entity).to(equal(childEntity));
-				expect(context.insertedObjects).to(contain(child));
-
-				expect(child.childID).to(beGreaterThanOrEqualTo(@3));
-				expect(child.childID).to(beLessThan(@6));
-
-				expect(child.parent1).to(equal(parent));
-				expect(child.parent2).to(beNil());
-			}
-
-			expect(@([context save:&error])).to(beTruthy());
-			expect(error).to(beNil());
-		});
-
-		it(@"should return an error if a model object could not be inserted", ^{
-			MTLFailureModel *failureModel = [MTLFailureModel modelWithDictionary:@{
-				@"notSupported": @"foobar"
-			} error:NULL];
-
-			__block NSError *error = nil;
-			NSManagedObject *failure =[MTLManagedObjectAdapter managedObjectFromModel:failureModel insertingIntoContext:context error:&error];
-
-			expect(failure).to(beNil());
-			expect(error).notTo(beNil());
-		});
-
-		it(@"should return an error if model doesn't validate for attribute description", ^{
-			MTLParentTestModel *parentModel = [MTLParentTestModel modelWithDictionary:@{} error:NULL];
-
-			NSError *error;
-			NSManagedObject *managedObject = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&error];
-
-			expect(managedObject).to(beNil());
-			expect(error).notTo(beNil());
-		});
-
-		it(@"should return nil and error with an illegal JSON mapping", ^{
-			MTLParent *parent = [MTLParent insertInManagedObjectContext:context];
-			expect(parent).notTo(beNil());
-
-			parent.string = @"foobar";
-
-			NSError *error = nil;
-			MTLIllegalManagedObjectMappingModel *model = [MTLManagedObjectAdapter modelOfClass:MTLIllegalManagedObjectMappingModel.class fromManagedObject:parent error:&error];
-			expect(model).to(beNil());
-			expect(error).notTo(beNil());
-			expect(error.domain).to(equal(MTLManagedObjectAdapterErrorDomain));
-			expect(@(error.code)).to(equal(@(MTLManagedObjectAdapterErrorInvalidManagedObjectMapping)));
-		});
-
-		it(@"should return an error if model doesn't validate for insert", ^{
-			MTLParentIncorrectTestModel *parentModel = [MTLParentIncorrectTestModel modelWithDictionary:@{} error:NULL];
-
-			NSError *error;
-			NSManagedObject *managedObject = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&error];
-
-			expect(managedObject).to(beNil());
-			expect(error).notTo(beNil());
-		});
-
-		it(@"should respect the uniqueness constraint", ^{
-			NSError *errorOne;
-			MTLParent *parentOne = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&errorOne];
-			expect(parentOne).notTo(beNil());
-			expect(errorOne).to(beNil());
-
-			NSError *errorTwo;
-			MTLParent *parentTwo = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&errorTwo];
-			expect(parentTwo).notTo(beNil());
-			expect(errorTwo).to(beNil());
-
-			expect(parentOne.objectID).to(equal(parentTwo.objectID));
-		});
-
-		it(@"should update relationships for an existing object", ^{
-			NSError *error;
-			MTLParent *parentOne = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&error];
-			expect(parentOne).notTo(beNil());
-			expect(error).to(beNil());
-			expect(@(parentOne.orderedChildren.count)).to(equal(@3));
-			expect(@(parentOne.unorderedChildren.count)).to(equal(@3));
-
-			MTLChild *child1Parent1 = parentOne.orderedChildren[0];
-			MTLChild *child2Parent1 = parentOne.orderedChildren[1];
-			MTLChild *child3Parent1 = parentOne.orderedChildren[2];
-
-			MTLParentTestModel *parentModelCopy = [parentModel copy];
-			[[parentModelCopy mutableOrderedSetValueForKey:@"orderedChildren"] removeObjectAtIndex:1];
-
-			MTLChildTestModel *childToDeleteModel = [parentModelCopy.unorderedChildren anyObject];
-			[[parentModelCopy mutableSetValueForKey:@"unorderedChildren"] removeObject:childToDeleteModel];
-
-			MTLParent *parentTwo = [MTLManagedObjectAdapter managedObjectFromModel:parentModelCopy insertingIntoContext:context error:&error];
-			expect(parentTwo).notTo(beNil());
-			expect(error).to(beNil());
-			expect(@(parentTwo.orderedChildren.count)).to(equal(@2));
-			expect(@(parentTwo.unorderedChildren.count)).to(equal(@2));
-
-			for (MTLChild *child in parentTwo.orderedChildren) {
-				expect(child.childID).notTo(equal(child2Parent1.childID));
-			}
-
-			for (MTLChild *child in parentTwo.unorderedChildren) {
-				expect(child.childID).notTo(equal(@(childToDeleteModel.childID)));
-			}
-
-			MTLChild *child1Parent2 = parentTwo.orderedChildren[0];
-			MTLChild *child2Parent2 = parentTwo.orderedChildren[1];
-			expect(child1Parent2).to(equal(child1Parent1));
-			expect(child2Parent2).to(equal(child3Parent1));
-		});
-
-		it(@"should try to merge existing values before overwriting data", ^{
-			NSError *error;
-			MTLParent *parentOne = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&error];
-			expect(parentOne).notTo(beNil());
-			expect(error).to(beNil());
-
-			NSDictionary *updates = @{
-				@"date": [NSDate date],
-				@"numberString": @"1234",
-				@"requiredString": @"We expect this string to be 'merged' after insertion"
-			};
-
-			MTLParentMergingTestModel *updatedParentModel = [MTLParentMergingTestModel modelWithDictionary:updates error:NULL];
-
-			expect(parentModel).notTo(beNil());
-
-			BOOL saveSuccessful = [context save:nil];
-			expect(@(saveSuccessful)).to(beTruthy());
-
-			NSString *initialValueOfRequiredString = updatedParentModel.requiredString;
-			MTLParent *updatedParentOne = [MTLManagedObjectAdapter managedObjectFromModel:updatedParentModel insertingIntoContext:context error:&error];
-			expect(updatedParentOne).notTo(beNil());
-			expect(updatedParentOne.string).notTo(equal(initialValueOfRequiredString));
-			expect(updatedParentOne.string).to(equal(@"merged"));
-		});
-	});
-});
-
-describe(@"with a main queue context", ^{
-	__block NSManagedObjectContext *context;
-
-	beforeEach(^{
-		context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
-		expect(context).notTo(beNil());
-
-		context.undoManager = nil;
-		context.persistentStoreCoordinator = persistentStoreCoordinator;
-	});
-
-	it(@"should not deadlock on the main thread", ^{
-		MTLParent *parent = [MTLParent insertInManagedObjectContext:context];
-		expect(parent).notTo(beNil());
-
-		parent.string = @"foobar";
-
-		NSError *error = nil;
-		MTLParentTestModel *parentModel = [MTLManagedObjectAdapter modelOfClass:MTLParentTestModel.class fromManagedObject:parent error:&error];
-		expect(parentModel).to(beAnInstanceOf(MTLParentTestModel.class));
-		expect(error).to(beNil());
-	});
-});
-
-describe(@"with a child that fails serialization", ^{
-	__block NSManagedObjectContext *context;
-
-	__block NSEntityDescription *parentEntity;
-	__block NSEntityDescription *childEntity;
-	__block MTLParentTestModel *parentModel;
-
-	beforeEach(^{
-		context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
-		expect(context).notTo(beNil());
-
-		context.undoManager = nil;
-		context.persistentStoreCoordinator = persistentStoreCoordinator;
-
-		parentEntity = [NSEntityDescription entityForName:@"Parent" inManagedObjectContext:context];
-		expect(parentEntity).notTo(beNil());
-
-		childEntity = [NSEntityDescription entityForName:@"BadChild" inManagedObjectContext:context];
-		expect(childEntity).notTo(beNil());
-
-		parentModel = [MTLParentTestModel modelWithDictionary:@{
-			@"date": [NSDate date],
-			@"numberString": @"1234",
-			@"requiredString": @"foobar"
-		} error:NULL];
-		expect(parentModel).notTo(beNil());
-
-		NSMutableArray *orderedChildren = [NSMutableArray array];
-
-		for (NSUInteger i = 3; i < 6; i++) {
-			MTLBadChildTestModel *child = [MTLBadChildTestModel modelWithDictionary:@{
-				@"childID": @(i)
-			} error:NULL];
-			expect(child).notTo(beNil());
-
-			[orderedChildren addObject:child];
-		}
-
-		parentModel.orderedChildren = orderedChildren;
-	});
-
-	it(@"should insert a managed object with children", ^{
-		__block NSError *error = nil;
-		MTLParent *parent = [MTLManagedObjectAdapter managedObjectFromModel:parentModel insertingIntoContext:context error:&error];
-		expect(parent).to(beNil());
-		expect(error).notTo(beNil());
-		expect(@([context save:&error])).to(beTruthy());
-	});
-});
-
-QuickSpecEnd

MantleTests/MTLModelSpec.m

@@ -103,6 +103,13 @@ describe(@"with a dictionary of values", ^{
 		expect(copiedModel).to(equal(model));
 		expect(copiedModel).notTo(beIdenticalTo(model));
 	});
+
+	it(@"should not consider -weakModel for equality", ^{
+		MTLTestModel *copiedModel = [model copy];
+		copiedModel.weakModel = nil;
+
+		expect(model).to(equal(copiedModel));
+	});
 });
 
 it(@"should fail to initialize if dictionary validation fails", ^{
@@ -128,6 +135,32 @@ it(@"should merge two models together", ^{
 	expect(@(target.count)).to(equal(@8));
 });
 
+it(@"should consider primitive properties permanent", ^{
+	expect(@([MTLStorageBehaviorModel storageBehaviorForPropertyWithKey:@"primitive"])).to(equal(@(MTLPropertyStoragePermanent)));
+});
+
+it(@"should consider object-type assign properties permanent", ^{
+	expect(@([MTLStorageBehaviorModel storageBehaviorForPropertyWithKey:@"assignProperty"])).to(equal(@(MTLPropertyStoragePermanent)));
+});
+
+it(@"should consider object-type strong properties permanent", ^{
+	expect(@([MTLStorageBehaviorModel storageBehaviorForPropertyWithKey:@"strongProperty"])).to(equal(@(MTLPropertyStoragePermanent)));
+});
+
+it(@"should ignore readonly properties without backing ivar", ^{
+	expect(@([MTLStorageBehaviorModel storageBehaviorForPropertyWithKey:@"notIvarBacked"])).to(equal(@(MTLPropertyStorageNone)));
+});
+
+it(@"should consider properties declared in subclass with storage in superclass permanent", ^{
+	expect(@([MTLStorageBehaviorModelSubclass storageBehaviorForPropertyWithKey:@"shadowedInSubclass"])).to(equal(@(MTLPropertyStoragePermanent)));
+	expect(@([MTLStorageBehaviorModelSubclass storageBehaviorForPropertyWithKey:@"declaredInProtocol"])).to(equal(@(MTLPropertyStoragePermanent)));
+});
+
+it(@"should ignore optional protocol properties not implemented", ^{
+	expect(@([MTLOptionalPropertyModel storageBehaviorForPropertyWithKey:@"optionalUnimplementedProperty"])).to(equal(@(MTLPropertyStorageNone)));
+	expect(@([MTLOptionalPropertyModel storageBehaviorForPropertyWithKey:@"optionalImplementedProperty"])).to(equal(@(MTLPropertyStoragePermanent)));
+});
+
 describe(@"merging with model subclasses", ^{
 	__block MTLTestModel *superclass;
 	__block MTLSubclassTestModel *subclass;
@@ -167,4 +200,5 @@ describe(@"merging with model subclasses", ^{
 	});
 });
 
+
 QuickSpecEnd

MantleTests/MTLPredefinedTransformerAdditionsSpec.m

@@ -9,6 +9,7 @@
 #import <Mantle/Mantle.h>
 #import <Nimble/Nimble.h>
 #import <Quick/Quick.h>
+#import "MTLTransformerErrorExamples.h"
 
 #import "MTLTestModel.h"
 
@@ -21,111 +22,161 @@ enum : NSInteger {
 
 QuickSpecBegin(MTLPredefinedTransformerAdditions)
 
-it(@"should define a URL value transformer", ^{
-	NSValueTransformer *transformer = [NSValueTransformer valueTransformerForName:MTLURLValueTransformerName];
-	expect(transformer).notTo(beNil());
-	expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+describe(@"The URL transformer", ^{
+	__block NSValueTransformer *transformer;
 
-	NSString *URLString = @"http://www.github.com/";
-	expect([transformer transformedValue:URLString]).to(equal([NSURL URLWithString:URLString]));
-	expect([transformer reverseTransformedValue:[NSURL URLWithString:URLString]]).to(equal(URLString));
+	beforeEach(^{
+		transformer = [NSValueTransformer valueTransformerForName:MTLURLValueTransformerName];
 
-	expect([transformer transformedValue:nil]).to(beNil());
-	expect([transformer reverseTransformedValue:nil]).to(beNil());
+		expect(transformer).notTo(beNil());
+		expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+	});
+
+	it(@"should convert NSStrings to NSURLs and back", ^{
+		NSString *URLString = @"http://www.github.com/";
+		expect([transformer transformedValue:URLString]).to(equal([NSURL URLWithString:URLString]));
+		expect([transformer reverseTransformedValue:[NSURL URLWithString:URLString]]).to(equal(URLString));
+
+		expect([transformer transformedValue:nil]).to(beNil());
+		expect([transformer reverseTransformedValue:nil]).to(beNil());
+	});
+
+	itBehavesLike(MTLTransformerErrorExamples, ^{
+		return @{
+			MTLTransformerErrorExamplesTransformer: transformer,
+			MTLTransformerErrorExamplesInvalidTransformationInput: @"not a valid URL",
+			MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+		};
+	});
 });
 
-it(@"should define an NSNumber boolean value transformer", ^{
-	// Back these NSNumbers with ints, rather than booleans,
-	// to ensure that the value transformers are actually transforming.
-	NSNumber *booleanYES = @(1);
-	NSNumber *booleanNO = @(0);
-
-	NSValueTransformer *transformer = [NSValueTransformer valueTransformerForName:MTLBooleanValueTransformerName];
-	expect(transformer).notTo(beNil());
-	expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
-
-	expect([transformer transformedValue:booleanYES]).to(equal([NSNumber numberWithBool:YES]));
-	expect([transformer transformedValue:booleanYES]).to(equal((id)kCFBooleanTrue));
-
-	expect([transformer reverseTransformedValue:booleanYES]).to(equal([NSNumber numberWithBool:YES]));
-	expect([transformer reverseTransformedValue:booleanYES]).to(equal((id)kCFBooleanTrue));
-
-	expect([transformer transformedValue:booleanNO]).to(equal([NSNumber numberWithBool:NO]));
-	expect([transformer transformedValue:booleanNO]).to(equal((id)kCFBooleanFalse));
-
-	expect([transformer reverseTransformedValue:booleanNO]).to(equal([NSNumber numberWithBool:NO]));
-	expect([transformer reverseTransformedValue:booleanNO]).to(equal((id)kCFBooleanFalse));
-
-	expect([transformer transformedValue:nil]).to(beNil());
-	expect([transformer reverseTransformedValue:nil]).to(beNil());
+describe(@"The UUID transformer", ^{
+	__block NSValueTransformer *transformer;
+	
+	beforeEach(^{
+		transformer = [NSValueTransformer valueTransformerForName:MTLUUIDValueTransformerName];
+		
+		expect(transformer).notTo(beNil());
+		expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+	});
+	
+	it(@"should convert NSStrings to NSUUIDs and back", ^{
+		NSString *UUIDString = @"4A275FBD-8217-4397-964B-403F4C2B8545";
+		expect([transformer transformedValue:UUIDString]).to(equal([[NSUUID alloc] initWithUUIDString:UUIDString]));
+		expect([transformer reverseTransformedValue:[[NSUUID alloc] initWithUUIDString:UUIDString]]).to(equal(UUIDString));
+		
+		expect([transformer transformedValue:nil]).to(beNil());
+		expect([transformer reverseTransformedValue:nil]).to(beNil());
+	});
+	
+	itBehavesLike(MTLTransformerErrorExamples, ^{
+		return @{
+			MTLTransformerErrorExamplesTransformer: transformer,
+			MTLTransformerErrorExamplesInvalidTransformationInput: @"not a valid UUID",
+			MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+		};
+	});
 });
 
-describe(@"JSON transformers", ^{
-	describe(@"dictionary transformer", ^{
-		__block NSValueTransformer *transformer;
+describe(@"The number transformer", ^{
+	__block NSValueTransformer *transformer;
 
-		__block MTLTestModel *model;
-		__block NSDictionary *JSONDictionary;
+	beforeEach(^{
+		transformer = [NSValueTransformer valueTransformerForName:MTLBooleanValueTransformerName];
+		expect(transformer).notTo(beNil());
+		expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+	});
 
+	it(@"it convert int- to boolean-backed NSNumbers and back", ^{
+		// Back these NSNumbers with ints, rather than booleans,
+		// to ensure that the value transformers are actually transforming.
+		NSNumber *booleanYES = @(1);
+		NSNumber *booleanNO = @(0);
+
+		expect([transformer transformedValue:booleanYES]).to(equal([NSNumber numberWithBool:YES]));
+		expect([transformer transformedValue:booleanYES]).to(beIdenticalTo((id)kCFBooleanTrue));
+
+		expect([transformer reverseTransformedValue:booleanYES]).to(equal([NSNumber numberWithBool:YES]));
+		expect([transformer reverseTransformedValue:booleanYES]).to(beIdenticalTo((id)kCFBooleanTrue));
+
+		expect([transformer transformedValue:booleanNO]).to(equal([NSNumber numberWithBool:NO]));
+		expect([transformer transformedValue:booleanNO]).to(beIdenticalTo((id)kCFBooleanFalse));
+
+		expect([transformer reverseTransformedValue:booleanNO]).to(equal([NSNumber numberWithBool:NO]));
+		expect([transformer reverseTransformedValue:booleanNO]).to(beIdenticalTo((id)kCFBooleanFalse));
+
+		expect([transformer transformedValue:nil]).to(beNil());
+		expect([transformer reverseTransformedValue:nil]).to(beNil());
+	});
+
+	itBehavesLike(MTLTransformerErrorExamples, ^{
+		return @{
+			MTLTransformerErrorExamplesTransformer: transformer,
+			MTLTransformerErrorExamplesInvalidTransformationInput: NSNull.null,
+			MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+		};
+	});
+});
+
+describe(@"+mtl_arrayMappingTransformerWithTransformer:", ^{
+	__block NSValueTransformer *transformer;
+
+	NSArray *URLStrings = @[
+		@"https://github.com/",
+		@"https://github.com/MantleFramework",
+		@"http://apple.com"
+	];
+	NSArray *URLs = @[
+		[NSURL URLWithString:@"https://github.com/"],
+		[NSURL URLWithString:@"https://github.com/MantleFramework"],
+		[NSURL URLWithString:@"http://apple.com"]
+	];
+
+	describe(@"when called with a reversible transformer", ^{
 		beforeEach(^{
-			model = [[MTLTestModel alloc] init];
-			JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:model];
-
-			transformer = [NSValueTransformer mtl_JSONDictionaryTransformerWithModelClass:MTLTestModel.class];
+			NSValueTransformer *appliedTransformer = [NSValueTransformer valueTransformerForName:MTLURLValueTransformerName];
+			transformer = [NSValueTransformer mtl_arrayMappingTransformerWithTransformer:appliedTransformer];
 			expect(transformer).notTo(beNil());
 		});
 
-		it(@"should transform a JSON dictionary into a model", ^{
-			expect([transformer transformedValue:JSONDictionary]).to(equal(model));
+		it(@"should allow reverse transformation", ^{
+			expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
 		});
 
-		it(@"should transform a model into a JSON dictionary", ^{
-			expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
-			expect([transformer reverseTransformedValue:model]).to(equal(JSONDictionary));
+		it(@"should apply the transformer to each element", ^{
+			expect([transformer transformedValue:URLStrings]).to(equal(URLs));
+		});
+
+		it(@"should apply the transformer to each element in reverse", ^{
+			expect([transformer reverseTransformedValue:URLs]).to(equal(URLStrings));
 		});
 	});
 
-	describe(@"external representation array transformer", ^{
-		__block NSValueTransformer *transformer;
-
-		__block NSArray *models;
-		__block NSArray *JSONDictionaries;
-
+	describe(@"when called with a non-reversible transformer", ^{
 		beforeEach(^{
-			NSMutableArray *uniqueModels = [NSMutableArray array];
-			NSMutableArray *mutableDictionaries = [NSMutableArray array];
-
-			for (NSUInteger i = 0; i < 10; i++) {
-				MTLTestModel *model = [[MTLTestModel alloc] init];
-				model.count = i;
-
-				[uniqueModels addObject:model];
-
-				NSDictionary *dict = [MTLJSONAdapter JSONDictionaryFromModel:model];
-				expect(dict).notTo(beNil());
-
-				[mutableDictionaries addObject:dict];
-			}
-
-			uniqueModels[2] = NSNull.null;
-			mutableDictionaries[2] = NSNull.null;
-
-			models = [uniqueModels copy];
-			JSONDictionaries = [mutableDictionaries copy];
-
-			transformer = [NSValueTransformer mtl_JSONArrayTransformerWithModelClass:MTLTestModel.class];
+			NSValueTransformer *appliedTransformer = [MTLValueTransformer transformerUsingForwardBlock:^(NSString *str, BOOL *success, NSError **error) {
+				return [NSURL URLWithString:str];
+			}];
+			transformer = [NSValueTransformer mtl_arrayMappingTransformerWithTransformer:appliedTransformer];
 			expect(transformer).notTo(beNil());
 		});
 
-		it(@"should transform JSON dictionaries into models", ^{
-			expect([transformer transformedValue:JSONDictionaries]).to(equal(models));
+		it(@"should not allow reverse transformation", ^{
+			expect(@([transformer.class allowsReverseTransformation])).to(beFalsy());
 		});
 
-		it(@"should transform models into JSON dictionaries", ^{
-			expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
-			expect([transformer reverseTransformedValue:models]).to(equal(JSONDictionaries));
+		it(@"should apply the transformer to each element", ^{
+			expect([transformer transformedValue:URLStrings]).to(equal(URLs));
 		});
 	});
+
+	itBehavesLike(MTLTransformerErrorExamples, ^{
+		return @{
+			MTLTransformerErrorExamplesTransformer: transformer,
+			MTLTransformerErrorExamplesInvalidTransformationInput: NSNull.null,
+			MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+		};
+	});
 });
 
 describe(@"value mapping transformer", ^{
@@ -170,4 +221,84 @@ describe(@"value mapping transformer", ^{
 	});
 });
 
+describe(@"date format transformer", ^{
+	__block NSValueTransformer<MTLTransformerErrorHandling> *transformer;
+
+	beforeEach(^{
+		transformer = [NSValueTransformer mtl_dateTransformerWithDateFormat:@"MMMM d, yyyy" calendar:[NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian] locale:[NSLocale localeWithLocaleIdentifier:@"en_US"] timeZone:[NSTimeZone timeZoneWithName:@"America/Los_Angeles"] defaultDate:nil];
+		expect(transformer).notTo(beNil());
+		expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+		expect([transformer transformedValue:nil]).to(beNil());
+		expect([transformer reverseTransformedValue:nil]).to(beNil());
+	});
+
+	it(@"should transform strings into dates", ^{
+		expect([transformer transformedValue:@"September 25, 2015"]).to(equal([NSDate dateWithTimeIntervalSince1970:1443164400]));
+	});
+
+	it(@"should transform dates into strings", ^{
+		expect([transformer reverseTransformedValue:[NSDate dateWithTimeIntervalSince1970:1183135260]]).to(equal(@"June 29, 2007"));
+	});
+
+	it(@"should surface date formatter error descriptions", ^{
+		__block NSError *error;
+		__block BOOL success = NO;
+		
+		expect([transformer transformedValue:@"September 37, 2015" success:&success error:&error]).to(beNil());
+		expect(@(success)).to(beFalsy());
+		expect(error).notTo(beNil());
+		expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+		expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+		expect(error.userInfo[NSLocalizedFailureReasonErrorKey]).notTo(beNil());
+	});
+
+	itBehavesLike(MTLTransformerErrorExamples, ^{
+		return @{
+			MTLTransformerErrorExamplesTransformer: transformer,
+			MTLTransformerErrorExamplesInvalidTransformationInput: NSNull.null,
+			MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+		};
+	});
+});
+
+describe(@"number format transformer", ^{
+	__block NSValueTransformer<MTLTransformerErrorHandling> *transformer;
+
+	beforeEach(^{
+		transformer = [NSValueTransformer mtl_numberTransformerWithNumberStyle:NSNumberFormatterDecimalStyle locale:[NSLocale localeWithLocaleIdentifier:@"en_US"]];
+		expect(transformer).notTo(beNil());
+		expect(@([transformer.class allowsReverseTransformation])).to(beTruthy());
+		expect([transformer transformedValue:nil]).to(beNil());
+		expect([transformer reverseTransformedValue:nil]).to(beNil());
+	});
+
+	it(@"should transform strings into numbers", ^{
+		expect([transformer transformedValue:@"0.12345"]).to(equal(@0.12345));
+	});
+
+	it(@"should transform numbers into strings", ^{
+		expect([transformer reverseTransformedValue:@12345.678]).to(equal(@"12,345.678"));
+	});
+
+	it(@"should surface number formatter error descriptions", ^{
+		__block NSError *error;
+		__block BOOL success = NO;
+
+		expect([transformer transformedValue:@"Apple" success:&success error:&error]).to(beNil());
+		expect(@(success)).to(beFalsy());
+		expect(error).notTo(beNil());
+		expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+		expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+		expect(error.userInfo[NSLocalizedFailureReasonErrorKey]).notTo(beNil());
+	});
+
+	itBehavesLike(MTLTransformerErrorExamples, ^{
+		return @{
+			MTLTransformerErrorExamplesTransformer: transformer,
+			MTLTransformerErrorExamplesInvalidTransformationInput: NSNull.null,
+			MTLTransformerErrorExamplesInvalidReverseTransformationInput: NSNull.null
+		};
+	});
+});
+
 QuickSpecEnd

MantleTests/MTLTestJSONAdapter.h

@@ -0,0 +1,17 @@
+//
+//  MTLTestJSONAdapter.h
+//  Mantle
+//
+//  Created by Robert Böhnke on 03/04/14.
+//  Copyright (c) 2014 GitHub. All rights reserved.
+//
+
+#import <Mantle/Mantle.h>
+
+// Adds a custom key "test" to constructed JSON.
+@interface MTLTestJSONAdapter : MTLJSONAdapter
+
+// These property keys are not serialized.
+@property (readwrite, nonatomic, strong) NSSet *ignoredPropertyKeys;
+
+@end

MantleTests/MTLTestJSONAdapter.m

@@ -0,0 +1,28 @@
+//
+//  MTLTestJSONAdapter.m
+//  Mantle
+//
+//  Created by Robert Böhnke on 03/04/14.
+//  Copyright (c) 2014 GitHub. All rights reserved.
+//
+
+#import "MTLTestJSONAdapter.h"
+
+@implementation MTLTestJSONAdapter
+
+- (NSSet *)serializablePropertyKeys:(NSSet *)propertyKeys forModel:(id<MTLJSONSerializing>)model {
+	NSMutableSet *copy = [propertyKeys mutableCopy];
+
+	[copy minusSet:self.ignoredPropertyKeys];
+
+	return copy;
+}
+
+- (NSDictionary *)JSONDictionaryFromModel:(id<MTLJSONSerializing>)model error:(NSError **)error {
+	NSDictionary *dictionary = [super JSONDictionaryFromModel:model error:error];
+	return [dictionary mtl_dictionaryByAddingEntriesFromDictionary:@{
+		@"test": @YES
+	}];
+}
+
+@end

MantleTests/MTLTestModel.h

@@ -12,6 +12,8 @@ extern NSString * const MTLTestModelErrorDomain;
 extern const NSInteger MTLTestModelNameTooLong;
 extern const NSInteger MTLTestModelNameMissing;
 
+
+
 @interface MTLEmptyTestModel : MTLModel
 @end
 
@@ -38,7 +40,7 @@ extern const NSInteger MTLTestModelNameMissing;
 // Should not be stored in the dictionary value or JSON.
 @property (nonatomic, copy, readonly) NSString *dynamicName;
 
-// Should not be stored in JSON.
+// Should not be stored in JSON, has MTLPropertyStorageTransitory.
 @property (nonatomic, weak) MTLEmptyTestModel *weakModel;
 
 @end
@@ -62,7 +64,7 @@ extern const NSInteger MTLTestModelNameMissing;
 @interface MTLSubstitutingTestModel : MTLModel <MTLJSONSerializing>
 @end
 
-@interface MTLValidationModel : MTLModel
+@interface MTLValidationModel : MTLModel <MTLJSONSerializing>
 
 // Defaults to nil, which is not considered valid.
 @property (nonatomic, copy) NSString *name;
@@ -73,6 +75,155 @@ extern const NSInteger MTLTestModelNameMissing;
 @interface MTLSelfValidatingModel : MTLValidationModel
 @end
 
-// Maps a non-existant property "name" to the "username" key in JSON.
-@interface MTLIllegalJSONMappingModel : MTLModel <MTLJSONSerializing>
+@interface MTLURLModel : MTLModel <MTLJSONSerializing>
+
+// Defaults to http://github.com.
+@property (nonatomic, strong) NSURL *URL;
+
+@end
+
+@interface MTLURLSubclassModel : MTLURLModel
+
+// Defaults to http://github.com/Mantle/Mantle.
+@property (nonatomic, strong) NSURL *otherURL;
+
+@end
+
+@interface MTLUUIDModel : MTLModel <MTLJSONSerializing>
+
+// Defaults to 4A275FBD-8217-4397-964B-403F4C2B8545
+@property (nonatomic, strong) NSUUID *UUID;
+
+@end
+
+@interface MTLUUIDSubclassModel : MTLUUIDModel
+
+// Defaults to 593246D2-A290-43D5-9070-A299A489AE29
+@property (nonatomic, strong) NSUUID *otherUUID;
+
+@end
+
+// Conforms to MTLJSONSerializing but does not inherit from the MTLModel class.
+@interface MTLConformingModel : NSObject <MTLJSONSerializing>
+
+@property (nonatomic, copy) NSString *name;
+
+@end
+
+@interface MTLStorageBehaviorModel : MTLModel
+
+@property (readonly, nonatomic, assign) BOOL primitive;
+
+@property (readonly, nonatomic, assign) id assignProperty;
+@property (readonly, nonatomic, weak) id weakProperty;
+@property (readonly, nonatomic, strong) id strongProperty;
+
+@property (readonly, nonatomic, strong) id shadowedInSubclass;
+@property (readonly, nonatomic, strong) id declaredInProtocol;
+
+@end
+
+@protocol MTLDateProtocol <NSObject>
+
+@property (readonly, nonatomic, strong) id declaredInProtocol;
+
+@end
+
+@interface MTLStorageBehaviorModelSubclass : MTLStorageBehaviorModel <MTLDateProtocol>
+
+@property (readonly, nonatomic, strong) id shadowedInSubclass;
+
+@end
+
+@interface MTLBoolModel : MTLModel <MTLJSONSerializing>
+
+@property (nonatomic, assign) BOOL flag;
+
+@end
+
+@interface MTLStringModel : MTLModel <MTLJSONSerializing>
+
+@property (readwrite, nonatomic, copy) NSString *string;
+
+@end
+
+@interface MTLIDModel : MTLModel <MTLJSONSerializing>
+
+@property (nonatomic, strong) id anyObject;
+
+@end
+
+@interface MTLNonPropertyModel : MTLModel <MTLJSONSerializing>
+
+- (NSURL *)homepage;
+
+@end
+
+@interface MTLMultiKeypathModel : MTLModel <MTLJSONSerializing>
+
+// This property is associated with the "location" and "length" keys in JSON.
+@property (readonly, nonatomic, assign) NSRange range;
+
+// This property is associated with the "nested.location" and "nested.length"
+// keys in JSON.
+@property (readonly, nonatomic, assign) NSRange nestedRange;
+
+@end
+
+@interface MTLClassClusterModel : MTLModel <MTLJSONSerializing>
+
+@property (readonly, nonatomic, copy) NSString *flavor;
+
+@end
+
+@interface MTLChocolateClassClusterModel : MTLClassClusterModel
+
+// Associated with the "chocolate_bitterness" JSON key and transformed to a
+// string.
+@property (readwrite, nonatomic, assign) NSUInteger bitterness;
+
+@end
+
+@interface MTLStrawberryClassClusterModel : MTLClassClusterModel
+
+// Associated with the "strawberry_freshness" JSON key.
+@property (readwrite, nonatomic, assign) NSUInteger freshness;
+
+@end
+
+
+@protocol MTLOptionalPropertyProtocol
+
+@optional
+@property (readwrite, nonatomic, strong) id optionalUnimplementedProperty;
+@property (readwrite, nonatomic, strong) id optionalImplementedProperty;
+
+@end
+
+@interface MTLOptionalPropertyModel : MTLModel <MTLOptionalPropertyProtocol>
+
+@property (readwrite, nonatomic, strong) id optionalImplementedProperty;
+
+@end
+
+
+@interface MTLRecursiveUserModel : MTLModel <MTLJSONSerializing>
+
+@property (nonatomic, copy, readonly) NSString *name;
+@property (nonatomic, copy, readonly) NSArray *groups;
+
+@end
+
+@interface MTLRecursiveGroupModel : MTLModel <MTLJSONSerializing>
+
+@property (nonatomic, readonly) MTLRecursiveUserModel *owner;
+@property (nonatomic, readonly) NSArray *users;
+@end
+
+@interface MTLPropertyDefaultAdapterModel : MTLModel<MTLJSONSerializing>
+
+@property (readwrite, nonatomic, strong) MTLEmptyTestModel *nonConformingMTLJSONSerializingProperty;
+@property (readwrite, nonatomic, strong) MTLTestModel *conformingMTLJSONSerializingProperty;
+@property (readwrite, nonatomic, strong) NSString *property;
+
 @end

MantleTests/MTLTestModel.m

@@ -6,7 +6,10 @@
 //  Copyright (c) 2012 GitHub. All rights reserved.
 //
 
+#import "NSDictionary+MTLManipulationAdditions.h"
+
 #import "MTLTestModel.h"
+#import "NSDictionary+MTLMappingAdditions.h"
 
 NSString * const MTLTestModelErrorDomain = @"MTLTestModelErrorDomain";
 const NSInteger MTLTestModelNameTooLong = 1;
@@ -57,19 +60,23 @@ static NSUInteger modelVersion = 1;
 #pragma mark MTLJSONSerializing
 
 + (NSDictionary *)JSONKeyPathsByPropertyKey {
-	return @{
+	NSMutableDictionary *mapping = [[NSDictionary mtl_identityPropertyMapWithModel:self] mutableCopy];
+
+	[mapping removeObjectForKey:@"weakModel"];
+	[mapping addEntriesFromDictionary:@{
 		@"name": @"username",
-		@"nestedName": @"nested.name",
-		@"weakModel": NSNull.null,
-	};
+		@"nestedName": @"nested.name"
+	}];
+
+	return mapping;
 }
 
 + (NSValueTransformer *)countJSONTransformer {
 	return [MTLValueTransformer
-		reversibleTransformerWithForwardBlock:^(NSString *str) {
+		transformerUsingForwardBlock:^(NSString *str, BOOL *success, NSError **error) {
 			return @(str.integerValue);
 		}
-		reverseBlock:^(NSNumber *num) {
+		reverseBlock:^(NSNumber *num, BOOL *success, NSError **error) {
 			return num.stringValue;
 		}];
 }
@@ -112,6 +119,16 @@ static NSUInteger modelVersion = 1;
 	};
 }
 
+#pragma mark Property Storage Behavior
+
++ (MTLPropertyStorage)storageBehaviorForPropertyWithKey:(NSString *)propertyKey {
+	if ([propertyKey isEqual:@"weakModel"]) {
+		return MTLPropertyStorageTransitory;
+	} else {
+		return [super storageBehaviorForPropertyWithKey:propertyKey];
+	}
+}
+
 #pragma mark Merging
 
 - (void)mergeCountFromModel:(MTLTestModel *)model {
@@ -136,7 +153,7 @@ static NSUInteger modelVersion = 1;
 @implementation MTLSubstitutingTestModel
 
 + (NSDictionary *)JSONKeyPathsByPropertyKey {
-	return @{};
+	return [NSDictionary mtl_identityPropertyMapWithModel:self];
 }
 
 + (Class)classForParsingJSONDictionary:(NSDictionary *)JSONDictionary {
@@ -153,6 +170,12 @@ static NSUInteger modelVersion = 1;
 
 @implementation MTLValidationModel
 
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return @{
+		@"name": @"name"
+	};
+}
+
 - (BOOL)validateName:(NSString **)name error:(NSError **)error {
 	if (*name != nil) return YES;
 	if (error != NULL) {
@@ -176,11 +199,375 @@ static NSUInteger modelVersion = 1;
 
 @end
 
-@implementation MTLIllegalJSONMappingModel
+@implementation MTLURLModel
+
+- (instancetype)init {
+	self = [super init];
+	if (self == nil) return nil;
+
+	self.URL = [NSURL URLWithString:@"http://github.com"];
+	return self;
+}
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return [NSDictionary mtl_identityPropertyMapWithModel:self];
+}
+
+@end
+
+@implementation MTLURLSubclassModel
+
+- (instancetype)init {
+	self = [super init];
+	if (self == nil) return nil;
+	
+	self.otherURL = [NSURL URLWithString:@"http://github.com/Mantle/Mantle"];
+	return self;
+}
+
++ (NSValueTransformer *)JSONTransformerForKey:(NSString *)key {
+	return @{
+		// Not provided transformer for self.URL
+		@"otherURL": [NSValueTransformer valueTransformerForName:MTLURLValueTransformerName],
+	}[key];
+}
+
+@end
+
+@implementation MTLUUIDModel
+
+- (instancetype)init {
+	self = [super init];
+	if (self == nil) return nil;
+	
+	self.UUID = [[NSUUID alloc] initWithUUIDString:@"4A275FBD-8217-4397-964B-403F4C2B8545"];
+	return self;
+}
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return [NSDictionary mtl_identityPropertyMapWithModel:self];
+}
+
+@end
+
+@implementation MTLUUIDSubclassModel
+
+- (instancetype)init {
+	self = [super init];
+	if (self == nil) return nil;
+	
+	self.otherUUID = [[NSUUID alloc] initWithUUIDString:@"593246D2-A290-43D5-9070-A299A489AE29"];
+	return self;
+}
+
++ (NSValueTransformer *)JSONTransformerForKey:(NSString *)key {
+	return @{
+		// Not provided transformer for self.UUID
+		@"otherUUID": [NSValueTransformer valueTransformerForName:MTLUUIDValueTransformerName],
+	}[key];
+}
+
+@end
+
+@implementation MTLBoolModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return [NSDictionary mtl_identityPropertyMapWithModel:self];
+}
+
+@end
+
+@implementation MTLStringModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return [NSDictionary mtl_identityPropertyMapWithModel:self];
+}
+
+@end
+
+@implementation MTLIDModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return [NSDictionary mtl_identityPropertyMapWithModel:self];
+}
+
+@end
+
+@implementation MTLNonPropertyModel
+
++ (NSSet *)propertyKeys {
+	return [NSSet setWithObject:@"homepage"];
+}
+
+- (NSURL *)homepage {
+	return [NSURL URLWithString:@"about:blank"];
+}
+
++ (MTLPropertyStorage)storageBehaviorForPropertyWithKey:(NSString *)propertyKey {
+	if ([propertyKey isEqual:@"homepage"]) {
+		return MTLPropertyStoragePermanent;
+	}
+
+	return [super storageBehaviorForPropertyWithKey:propertyKey];
+}
+
+#pragma mark - MTLJSONSerializing
 
 + (NSDictionary *)JSONKeyPathsByPropertyKey {
 	return @{
-		@"name": @"username"
+		@"homepage": @"homepage"
+	};
+}
+
+@end
+
+@interface MTLConformingModel ()
+
+- (instancetype)initWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error;
+
+@end
+
+@implementation MTLConformingModel
+
+#pragma mark Lifecycle
+
++ (instancetype)modelWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error {
+	return [[self alloc] initWithDictionary:dictionaryValue error:error];
+}
+
+- (instancetype)initWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error {
+	self = [super init];
+	if (self == nil) return nil;
+
+	_name = dictionaryValue[@"name"];
+
+	return self;
+}
+
+- (BOOL)validate:(NSError **)error {
+	return YES;
+}
+
+#pragma mark MTLModel
+
+- (NSDictionary *)dictionaryValue {
+	if (self.name == nil) return @{};
+
+	return @{
+		@"name": self.name
+	};
+}
+
++ (NSSet *)propertyKeys {
+	return [NSSet setWithObject:@"name"];
+}
+
+- (void)mergeValueForKey:(NSString *)key fromModel:(id<MTLModel>)model {
+	if ([key isEqualToString:@"name"]) {
+		self.name = [model dictionaryValue][@"name"];
+	}
+}
+
+- (void)mergeValuesForKeysFromModel:(id<MTLModel>)model {
+	self.name = [model dictionaryValue][@"name"];
+}
+
+#pragma mark MTLJSONSerializing
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return @{
+		@"name": @"name"
+	};
+}
+
+#pragma mark NSObject
+
+- (NSUInteger)hash {
+	return self.name.hash;
+}
+
+- (BOOL)isEqual:(MTLConformingModel *)model {
+	if (self == model) return YES;
+	if (![model isMemberOfClass:self.class]) return NO;
+
+	return self.name == model.name || [self.name isEqual:model.name];
+}
+
+#pragma mark NSCopying
+
+- (id)copyWithZone:(NSZone *)zone {
+	return self;
+}
+
+@end
+
+@implementation MTLStorageBehaviorModel
+
+- (id)notIvarBacked {
+	return self;
+}
+
+@end
+
+@implementation MTLStorageBehaviorModelSubclass
+
+@dynamic shadowedInSubclass;
+
+@end
+
+@implementation MTLMultiKeypathModel
+
+#pragma mark MTLJSONSerializing
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return @{
+		@"range": @[ @"location", @"length" ],
+		@"nestedRange": @[ @"nested.location", @"nested.length" ]
+	};
+}
+
++ (NSValueTransformer *)rangeJSONTransformer {
+	return [MTLValueTransformer
+		transformerUsingForwardBlock:^(NSDictionary *value, BOOL *success, NSError **error) {
+			NSUInteger location = [value[@"location"] unsignedIntegerValue];
+			NSUInteger length = [value[@"length"] unsignedIntegerValue];
+
+			return [NSValue valueWithRange:NSMakeRange(location, length)];
+		} reverseBlock:^(NSValue *value, BOOL *success, NSError **error) {
+			NSRange range = value.rangeValue;
+
+			return @{
+				@"location": @(range.location),
+				@"length": @(range.length)
+			};
+		}];
+}
+
++ (NSValueTransformer *)nestedRangeJSONTransformer {
+	return [MTLValueTransformer
+		transformerUsingForwardBlock:^(NSDictionary *value, BOOL *success, NSError **error) {
+			NSUInteger location = [value[@"nested.location"] unsignedIntegerValue];
+			NSUInteger length = [value[@"nested.length"] unsignedIntegerValue];
+
+			return [NSValue valueWithRange:NSMakeRange(location, length)];
+		} reverseBlock:^(NSValue *value, BOOL *success, NSError **error) {
+			NSRange range = value.rangeValue;
+
+			return @{
+				@"nested.location": @(range.location),
+				@"nested.length": @(range.length)
+			};
+		}];
+}
+@end
+
+@implementation MTLClassClusterModel : MTLModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return @{
+		@"flavor": @"flavor"
+	};
+}
+
++ (Class)classForParsingJSONDictionary:(NSDictionary *)JSONDictionary {
+	if ([JSONDictionary[@"flavor"] isEqualToString:@"chocolate"]) {
+		return MTLChocolateClassClusterModel.class;
+	}
+
+	if ([JSONDictionary[@"flavor"] isEqualToString:@"strawberry"]) {
+		return MTLStrawberryClassClusterModel.class;
+	}
+
+	return nil;
+}
+
+@end
+
+@implementation MTLChocolateClassClusterModel : MTLClassClusterModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return [[super JSONKeyPathsByPropertyKey] mtl_dictionaryByAddingEntriesFromDictionary:@{
+		@"bitterness": @"chocolate_bitterness"
+	}];
+}
+
+- (NSString *)flavor {
+	return @"chocolate";
+}
+
++ (NSValueTransformer *)bitternessJSONTransformer {
+	return [MTLValueTransformer
+		transformerUsingForwardBlock:^(NSString *string, BOOL *success, NSError **error) {
+			NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
+
+			return [formatter numberFromString:string];
+		}
+		reverseBlock:^(NSNumber *value, BOOL *success, NSError **error) {
+			return [value description];
+		}];
+}
+
+@end
+
+@implementation MTLStrawberryClassClusterModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return [[super JSONKeyPathsByPropertyKey] mtl_dictionaryByAddingEntriesFromDictionary:@{
+		@"freshness": @"strawberry_freshness"
+	}];
+}
+
+- (NSString *)flavor {
+	return @"strawberry";
+}
+
+@end
+
+@implementation MTLOptionalPropertyModel
+
+@end
+
+@implementation MTLRecursiveUserModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return @{
+		@"name": @"name",
+		@"groups": @"groups",
+	};
+}
+
++ (NSValueTransformer *)groupsJSONTransformer {
+	return [MTLJSONAdapter arrayTransformerWithModelClass:MTLRecursiveGroupModel.class];
+}
+
+@end
+
+@implementation MTLRecursiveGroupModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return @{
+		@"owner": @"owner",
+		@"users": @"users",
+	};
+}
+
++ (NSValueTransformer *)ownerJSONTransformer {
+	return [MTLJSONAdapter dictionaryTransformerWithModelClass:MTLRecursiveUserModel.class];
+}
+
++ (NSValueTransformer *)usersJSONTransformer {
+	return [MTLJSONAdapter arrayTransformerWithModelClass:MTLRecursiveUserModel.class];
+}
+
+@end
+
+@implementation MTLPropertyDefaultAdapterModel
+
++ (NSDictionary *)JSONKeyPathsByPropertyKey {
+	return @{
+		@"conformingMTLJSONSerializingProperty": @"conformingMTLJSONSerializingProperty",
+		@"nonConformingMTLJSONSerializingProperty": @"nonConformingMTLJSONSerializingProperty",
+		@"property": @"property"
 	};
 }
 

MantleTests/MTLTransformerErrorExamples.h

@@ -0,0 +1,15 @@
+//
+//  MTLTransformerErrorExamples.h
+//  Mantle
+//
+//  Created by Robert Böhnke on 10/9/13.
+//  Copyright (c) 2013 GitHub. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+extern NSString * const MTLTransformerErrorExamples;
+
+extern NSString * const MTLTransformerErrorExamplesTransformer;
+extern NSString * const MTLTransformerErrorExamplesInvalidTransformationInput;
+extern NSString * const MTLTransformerErrorExamplesInvalidReverseTransformationInput;

MantleTests/MTLTransformerErrorExamples.m

@@ -0,0 +1,65 @@
+//
+//  MTLTransformerErrorExamples.m
+//  Mantle
+//
+//  Created by Robert Böhnke on 10/9/13.
+//  Copyright (c) 2013 GitHub. All rights reserved.
+//
+
+#import <Quick/Quick.h>
+#import <Nimble/Nimble.h>
+#import "MTLTransformerErrorExamples.h"
+
+#import "MTLTransformerErrorHandling.h"
+
+NSString * const MTLTransformerErrorExamples = @"MTLTransformerErrorExamples";
+
+NSString * const MTLTransformerErrorExamplesTransformer = @"MTLTransformerErrorExamplesTransformer";
+NSString * const MTLTransformerErrorExamplesInvalidTransformationInput = @"MTLTransformerErrorExamplesInvalidTransformationInput";
+NSString * const MTLTransformerErrorExamplesInvalidReverseTransformationInput = @"MTLTransformerErrorExamplesInvalidReverseTransformationInput";
+
+QuickConfigurationBegin(MTLTransformerErrorExamplesConfiguration)
+
++ (void)configure:(Configuration *)configuration {
+	sharedExamples(MTLTransformerErrorExamples, ^(QCKDSLSharedExampleContext data) {
+		__block NSValueTransformer<MTLTransformerErrorHandling> *transformer;
+		__block id invalidTransformationInput;
+		__block id invalidReverseTransformationInput;
+
+		beforeEach(^{
+			transformer = data()[MTLTransformerErrorExamplesTransformer];
+			invalidTransformationInput = data()[MTLTransformerErrorExamplesInvalidTransformationInput];
+			invalidReverseTransformationInput = data()[MTLTransformerErrorExamplesInvalidReverseTransformationInput];
+
+			expect(@([transformer conformsToProtocol:@protocol(MTLTransformerErrorHandling)])).to(beTruthy());
+		});
+
+		it(@"should return errors occurring during transformation", ^{
+			__block NSError *error;
+			__block BOOL success = NO;
+
+			expect([transformer transformedValue:invalidTransformationInput success:&success error:&error]).to(beNil());
+			expect(@(success)).to(beFalsy());
+			expect(error).notTo(beNil());
+			expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+			expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+			expect(error.userInfo[MTLTransformerErrorHandlingInputValueErrorKey]).to(equal(invalidTransformationInput));
+		});
+
+		it(@"should return errors occurring during reverse transformation", ^{
+			if (![transformer.class allowsReverseTransformation]) return;
+
+			__block NSError *error;
+			__block BOOL success = NO;
+
+			expect([transformer reverseTransformedValue:invalidReverseTransformationInput success:&success error:&error]).to(beNil());
+			expect(@(success)).to(beFalsy());
+			expect(error).notTo(beNil());
+			expect(error.domain).to(equal(MTLTransformerErrorHandlingErrorDomain));
+			expect(@(error.code)).to(equal(@(MTLTransformerErrorHandlingErrorInvalidInput)));
+			expect(error.userInfo[MTLTransformerErrorHandlingInputValueErrorKey]).to(equal(invalidReverseTransformationInput));
+		});
+	});
+}
+
+QuickConfigurationEnd

MantleTests/MTLValueTransformerSpec.m

@@ -13,7 +13,7 @@
 QuickSpecBegin(MTLValueTransformerSpec)
 
 it(@"should return a forward transformer with a block", ^{
-	MTLValueTransformer *transformer = [MTLValueTransformer transformerWithBlock:^(NSString *str) {
+	MTLValueTransformer *transformer = [MTLValueTransformer transformerUsingForwardBlock:^(NSString *str, BOOL *success, NSError **error) {
 		return [str stringByAppendingString:@"bar"];
 	}];
 
@@ -25,7 +25,7 @@ it(@"should return a forward transformer with a block", ^{
 });
 
 it(@"should return a reversible transformer with a block", ^{
-	MTLValueTransformer *transformer = [MTLValueTransformer reversibleTransformerWithBlock:^(NSString *str) {
+	MTLValueTransformer *transformer = [MTLValueTransformer transformerUsingReversibleBlock:^(NSString *str, BOOL *success, NSError **error) {
 		return [str stringByAppendingString:@"bar"];
 	}];
 
@@ -38,10 +38,10 @@ it(@"should return a reversible transformer with a block", ^{
 
 it(@"should return a reversible transformer with forward and reverse blocks", ^{
 	MTLValueTransformer *transformer = [MTLValueTransformer
-		reversibleTransformerWithForwardBlock:^(NSString *str) {
+		transformerUsingForwardBlock:^(NSString *str, BOOL *success, NSError **error) {
 			return [str stringByAppendingString:@"bar"];
 		}
-		reverseBlock:^(NSString *str) {
+		reverseBlock:^(NSString *str, BOOL *success, NSError **error) {
 			return [str substringToIndex:str.length - 3];
 		}];
 

MantleTests/TestModel.xcdatamodeld/TestModel.xcdatamodel/contents

@@ -1,25 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<model userDefinedModelVersionIdentifier="" type="com.apple.IDECoreDataModeler.DataModel" documentVersion="1.0" lastSavedToolsVersion="3396" systemVersion="13A598" minimumToolsVersion="Xcode 4.3" macOSVersion="Automatic" iOSVersion="Automatic">
-    <entity name="BadChild" representedClassName="MTLChild" syncable="YES">
-        <attribute name="childID_BROKEN" attributeType="Integer 16" defaultValueString="0" indexed="YES" syncable="YES"/>
-    </entity>
-    <entity name="Child" representedClassName="MTLChild" syncable="YES">
-        <attribute name="childID" attributeType="Integer 16" defaultValueString="0" indexed="YES" syncable="YES"/>
-        <relationship name="parent1" optional="YES" minCount="1" maxCount="1" deletionRule="Nullify" destinationEntity="Parent" inverseName="unorderedChildren" inverseEntity="Parent" syncable="YES"/>
-        <relationship name="parent2" optional="YES" minCount="1" maxCount="1" deletionRule="Nullify" destinationEntity="Parent" inverseName="orderedChildren" inverseEntity="Parent" syncable="YES"/>
-    </entity>
-    <entity name="Empty" syncable="YES"/>
-    <entity name="Parent" representedClassName="MTLParent" syncable="YES">
-        <attribute name="date" optional="YES" attributeType="Date" syncable="YES"/>
-        <attribute name="number" optional="YES" attributeType="Integer 64" defaultValueString="0" syncable="YES"/>
-        <attribute name="string" attributeType="String" syncable="YES"/>
-        <relationship name="orderedChildren" optional="YES" toMany="YES" deletionRule="Nullify" ordered="YES" destinationEntity="Child" inverseName="parent2" inverseEntity="Child" syncable="YES"/>
-        <relationship name="unorderedChildren" optional="YES" toMany="YES" deletionRule="Nullify" destinationEntity="Child" inverseName="parent1" inverseEntity="Child" syncable="YES"/>
-    </entity>
-    <elements>
-        <element name="Child" positionX="0" positionY="0" width="0" height="0"/>
-        <element name="Empty" positionX="0" positionY="0" width="0" height="0"/>
-        <element name="Parent" positionX="0" positionY="0" width="0" height="0"/>
-        <element name="BadChild" positionX="0" positionY="0" width="0" height="0"/>
-    </elements>
-</model>

README.md

@@ -1,4 +1,4 @@
-# Mantle
+# Mantle [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 
 Mantle makes it easy to write a simple model layer for your Cocoa or Cocoa Touch
 application.
@@ -209,6 +209,8 @@ typedef enum : NSUInteger {
     return @{
         @"URL": @"url",
         @"HTMLURL": @"html_url",
+        @"number": @"number",
+        @"state": @"state",
         @"reporterLogin": @"user.login",
         @"assignee": @"assignee",
         @"updatedAt": @"updated_at"
@@ -231,13 +233,13 @@ typedef enum : NSUInteger {
 }
 
 + (NSValueTransformer *)assigneeJSONTransformer {
-    return [NSValueTransformer mtl_JSONDictionaryTransformerWithModelClass:GHUser.class];
+    return [MTLJSONAdapter dictionaryTransformerWithModelClass:GHUser.class];
 }
 
 + (NSValueTransformer *)updatedAtJSONTransformer {
-    return [MTLValueTransformer reversibleTransformerWithForwardBlock:^(NSString *str) {
-        return [self.dateFormatter dateFromString:str];
-    } reverseBlock:^(NSDate *date) {
+    return [MTLValueTransformer transformerUsingForwardBlock:^id(NSString *dateString, BOOL *success, NSError *__autoreleasing *error) {
+        return [self.dateFormatter dateFromString:dateString];
+    } reverseBlock:^id(NSDate *date, BOOL *success, NSError *__autoreleasing *error) {
         return [self.dateFormatter stringFromDate:date];
     }];
 }
@@ -270,9 +272,9 @@ it easy to specify how new model data should be integrated.
 > There's no way to turn a `GHIssue` _back_ into JSON.
 
 This is where reversible transformers really come in handy. `+[MTLJSONAdapter
-JSONDictionaryFromModel:]` can transform any model object conforming to
+JSONDictionaryFromModel:error:]` can transform any model object conforming to
 `<MTLJSONSerializing>` back into a JSON dictionary. `+[MTLJSONAdapter
-JSONArrayForModels:]` is the same but turns an array of model objects into an JSON array of dictionaries.
+JSONArrayFromModels:error:]` is the same but turns an array of model objects into an JSON array of dictionaries.
 
 > If the interface of `GHIssue` changes down the road, existing archives might break.
 
@@ -292,14 +294,14 @@ XYUser *user = [MTLJSONAdapter modelOfClass:XYUser.class fromJSONDictionary:JSON
 ```
 
 ```objc
-NSDictionary *JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:user];
+NSError *error = nil;
+NSDictionary *JSONDictionary = [MTLJSONAdapter JSONDictionaryFromModel:user error:&error];
 ```
 
 ### `+JSONKeyPathsByPropertyKey`
 
 The dictionary returned by this method specifies how your model object's
-properties map to the keys in the JSON representation. Properties that map to
-`NSNull` will not be present in the JSON representation, for example:
+properties map to the keys in the JSON representation, for example:
 
 ```objc
 
@@ -317,8 +319,8 @@ properties map to the keys in the JSON representation. Properties that map to
 
 + (NSDictionary *)JSONKeyPathsByPropertyKey {
     return @{
-        @"createdAt": @"created_at",
-        @"meUser": NSNull.null
+        @"name": @"name",
+        @"createdAt": @"created_at"
     };
 }
 
@@ -337,8 +339,7 @@ properties map to the keys in the JSON representation. Properties that map to
 In this example, the `XYUser` class declares four properties that Mantle
 handles in different ways:
 
-- `name` is implicitly mapped to a key of the same name in the JSON
-  representation.
+- `name` is mapped to a key of the same name in the JSON representation.
 - `createdAt` is converted to its snake case equivalent.
 - `meUser` is not serialized into JSON.
 - `helper` is initialized exactly once after JSON deserialization.
@@ -346,6 +347,9 @@ handles in different ways:
 Use `-[NSDictionary mtl_dictionaryByAddingEntriesFromDictionary:]` if your
 model's superclass also implements `MTLJSONSerializing` to merge their mappings.
 
+If you'd like to map all properties of a Model class to themselves, you can use
+the `+[NSDictionary mtl_identityPropertyMapWithModel:]` helper method.
+
 When deserializing JSON using
 `+[MTLJSONAdapter modelOfClass:fromJSONDictionary:error:]`, JSON keys that don't
 correspond to a property name or have an explicit mapping are ignored:
@@ -378,16 +382,17 @@ deserializing from JSON.
 }
 ```
 
+`key` is the key that applies to your model object; not the original JSON key. Keep this in mind if you transform the key names using `+JSONKeyPathsByPropertyKey`.
+
 For added convenience, if you implement `+<key>JSONTransformer`,
 `MTLJSONAdapter` will use the result of that method instead. For example, dates
 that are commonly represented as strings in JSON can be transformed to `NSDate`s
 like so:
 
 ```objc
-+ (NSValueTransformer *)createdAtJSONTransformer {
-    return [MTLValueTransformer reversibleTransformerWithForwardBlock:^(NSString *str) {
-        return [self.dateFormatter dateFromString:str];
-    } reverseBlock:^(NSDate *date) {
+    return [MTLValueTransformer transformerUsingForwardBlock:^id(NSString *dateString, BOOL *success, NSError *__autoreleasing *error) {
+        return [self.dateFormatter dateFromString:dateString];
+    } reverseBlock:^id(NSDate *date, BOOL *success, NSError *__autoreleasing *error) {
         return [self.dateFormatter stringFromDate:date];
     }];
 }
@@ -467,32 +472,24 @@ in memory at once, Core Data may be a better choice.
 
 ## System Requirements
 
-Mantle supports OS X 10.7+ and iOS 5.0+.
+Mantle supports OS X 10.9+ and iOS 8.0+.
 
 ## Importing Mantle
 
 To add Mantle to your application:
 
  1. Add the Mantle repository as a submodule of your application's repository.
- 1. Run `script/bootstrap` from within the Mantle folder.
- 1. Drag and drop `Mantle.xcodeproj` into your application's Xcode project or
-    workspace.
- 1. On the "Build Phases" tab of your application target, add Mantle to the
-    "Link Binary With Libraries" phase.
-    * **On iOS**, add `libMantle.a`.
-    * **On OS X**, add `Mantle.framework`. Mantle must also be added to any
-      "Copy Frameworks" build phase. If you don't already have one, simply add a
-      "Copy Files" build phase and target the "Frameworks" destination.
- 1. Add `"$(BUILD_ROOT)/../IntermediateBuildFilesPath/UninstalledProducts/include" $(inherited)`
-    to the "Header Search Paths" build setting (this is only
-    necessary for archive builds, but it has no negative effect otherwise).
- 1. **For iOS targets**, add `-ObjC` to the "Other Linker Flags" build setting.
- 1. **If you added Mantle to a project (not a workspace)**, you will also need
-    to add the appropriate Mantle target to the "Target Dependencies" of your
-    application.
+ 1. Run `git submodule update --init --recursive` from within the Mantle folder.
+ 1. Drag and drop `Mantle.xcodeproj` into your application's Xcode project.
+ 1. On the "General" tab of your application target, add `Mantle.framework` to the "Embedded Binaries".
+
+[Carthage](https://github.com/Carthage/Carthage) users can simply add Mantle to their `Cartfile`:
+```
+github "Mantle/Mantle"
+```
 
 If you would prefer to use [CocoaPods](http://cocoapods.org), there are some
-[Mantle podspecs](https://github.com/CocoaPods/Specs/tree/master/Specs/Mantle) that
+[Mantle podspecs](https://github.com/CocoaPods/Specs/tree/master/Specs/5/d/c/Mantle) that
 have been generously contributed by third parties.
 
 If you’re instead developing Mantle on its own, use the `Mantle.xcworkspace` file.

script/LICENSE.md

@@ -1,18 +0,0 @@
-**Copyright (c) 2013 Justin Spahr-Summers**
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of
-this software and associated documentation files (the "Software"), to deal in
-the Software without restriction, including without limitation the rights to
-use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
-the Software, and to permit persons to whom the Software is furnished to do so,
-subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
-FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
-COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
-IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
-CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

script/README.md

@@ -1,82 +0,0 @@
-# objc-build-scripts
-
-This project is a collection of scripts created with two goals:
-
- 1. To standardize how Objective-C projects are bootstrapped after cloning
- 1. To easily build Objective-C projects on continuous integration servers
-
-## Scripts
-
-Right now, there are two important scripts: [`bootstrap`](#bootstrap) and
-[`cibuild`](#cibuild). Both are Bash scripts, to maximize compatibility and
-eliminate pesky system configuration issues (like setting up a working Ruby
-environment).
-
-The structure of the scripts on disk is meant to follow that of a typical Ruby
-project:
-
-```
-script/
-    bootstrap
-    cibuild
-```
-
-### bootstrap
-
-This script is responsible for bootstrapping (initializing) your project after
-it's been checked out. Here, you should install or clone any dependencies that
-are required for a working build and development environment.
-
-By default, the script will verify that [xctool][] is installed, then initialize
-and update submodules recursively. If any submodules contain `script/bootstrap`,
-that will be run as well.
-
-To check that other tools are installed, you can set the `REQUIRED_TOOLS`
-environment variable before running `script/bootstrap`, or edit it within the
-script directly. Note that no installation is performed automatically, though
-this can always be added within your specific project.
-
-### cibuild
-
-This script is responsible for building the project, as you would want it built
-for continuous integration. This is preferable to putting the logic on the CI
-server itself, since it ensures that any changes are versioned along with the
-source.
-
-By default, the script will run [`bootstrap`](#bootstrap), look for any Xcode
-workspace or project in the working directory, then build all targets/schemes
-(as found by `xcodebuild -list`) using [xctool][].
-
-You can also specify the schemes to build by passing them into the script:
-
-```sh
-script/cibuild ReactiveCocoa-Mac ReactiveCocoa-iOS
-```
-
-As with the `bootstrap` script, there are several environment variables that can
-be used to customize behavior. They can be set on the command line before
-invoking the script, or the defaults changed within the script directly.
-
-## Getting Started
-
-To add the scripts to your project, read the contents of this repository into
-a `script` folder:
-
-```
-$ git remote add objc-build-scripts https://github.com/jspahrsummers/objc-build-scripts.git
-$ git fetch objc-build-scripts
-$ git read-tree --prefix=script/ -u objc-build-scripts/master
-```
-
-Then commit the changes, to incorporate the scripts into your own repository's
-history. You can also freely tweak the scripts for your specific project's
-needs.
-
-To merge in upstream changes later:
-
-```
-$ git fetch -p objc-build-scripts
-$ git merge --ff --squash -Xsubtree=script objc-build-scripts/master
-```
-
-[xctool]: https://github.com/facebook/xctool

script/bootstrap

@@ -1,80 +0,0 @@
-#!/bin/bash
-
-export SCRIPT_DIR=$(dirname "$0")
-
-##
-## Configuration Variables
-##
-
-config ()
-{
-    # A whitespace-separated list of executables that must be present and locatable.
-    : ${REQUIRED_TOOLS="xctool"}
-
-    export REQUIRED_TOOLS
-}
-
-##
-## Bootstrap Process
-##
-
-main ()
-{
-    config
-
-    if [ -n "$REQUIRED_TOOLS" ]
-    then
-        echo "*** Checking dependencies..."
-        check_deps
-    fi
-
-    local submodules=$(git submodule status)
-    local result=$?
-
-    if [ "$result" -ne "0" ]
-    then
-        exit $result
-    fi
-
-    if [ -n "$submodules" ]
-    then
-        echo "*** Updating submodules..."
-        update_submodules
-    fi
-}
-
-check_deps ()
-{
-    for tool in $REQUIRED_TOOLS
-    do
-        which -s "$tool"
-        if [ "$?" -ne "0" ]
-        then
-            echo "*** Error: $tool not found. Please install it and bootstrap again."
-            exit 1
-        fi
-    done
-}
-
-bootstrap_submodule ()
-{
-    local bootstrap="script/bootstrap"
-
-    if [ -e "$bootstrap" ]
-    then
-        echo "*** Bootstrapping $name..."
-        "$bootstrap" >/dev/null
-    else
-        update_submodules
-    fi
-}
-
-update_submodules ()
-{
-    git submodule sync --quiet && git submodule update --init && git submodule foreach --quiet bootstrap_submodule
-}
-
-export -f bootstrap_submodule
-export -f update_submodules
-
-main

script/cibuild

@@ -1,153 +0,0 @@
-#!/bin/bash
-
-export SCRIPT_DIR=$(dirname "$0")
-
-##
-## Configuration Variables
-##
-
-SCHEMES="$@"
-
-config ()
-{
-    # The workspace to build.
-    #
-    # If not set and no workspace is found, the -workspace flag will not be passed
-    # to `xctool`.
-    #
-    # Only one of `XCWORKSPACE` and `XCODEPROJ` needs to be set. The former will
-    # take precedence.
-    : ${XCWORKSPACE=$(find_pattern "*.xcworkspace")}
-
-    # The project to build.
-    #
-    # If not set and no project is found, the -project flag will not be passed
-    # to `xctool`.
-    #
-    # Only one of `XCWORKSPACE` and `XCODEPROJ` needs to be set. The former will
-    # take precedence.
-    : ${XCODEPROJ=$(find_pattern "*.xcodeproj")}
-
-    # A bootstrap script to run before building.
-    #
-    # If this file does not exist, it is not considered an error.
-    : ${BOOTSTRAP="$SCRIPT_DIR/bootstrap"}
-
-    # Extra options to pass to xctool.
-    : ${XCTOOL_OPTIONS="RUN_CLANG_STATIC_ANALYZER=NO"}
-
-    # A whitespace-separated list of default schemes to build.
-    #
-    # Individual names can be quoted to avoid word splitting.
-    : ${SCHEMES:=$(xcodebuild -list -project "$XCODEPROJ" 2>/dev/null | awk -f "$SCRIPT_DIR/schemes.awk")}
-
-    export XCWORKSPACE
-    export XCODEPROJ
-    export BOOTSTRAP
-    export XCTOOL_OPTIONS
-    export SCHEMES
-}
-
-##
-## Build Process
-##
-
-main ()
-{
-    config
-
-    if [ -f "$BOOTSTRAP" ]
-    then
-        echo "*** Bootstrapping..."
-        "$BOOTSTRAP" || exit $?
-    fi
-
-    echo "*** The following schemes will be built:"
-    echo "$SCHEMES" | xargs -n 1 echo "  "
-    echo
-
-    echo "$SCHEMES" | xargs -n 1 | (
-        local status=0
-
-        while read scheme
-        do
-            build_scheme "$scheme" || status=1
-        done
-
-        exit $status
-    )
-}
-
-find_pattern ()
-{
-    ls -d $1 2>/dev/null | head -n 1
-}
-
-run_xctool ()
-{
-    if [ -n "$XCWORKSPACE" ]
-    then
-        xctool -workspace "$XCWORKSPACE" $XCTOOL_OPTIONS "$@" 2>&1
-    elif [ -n "$XCODEPROJ" ]
-    then
-        xctool -project "$XCODEPROJ" $XCTOOL_OPTIONS "$@" 2>&1
-    else
-        echo "*** No workspace or project file found."
-        exit 1
-    fi
-}
-
-parse_build ()
-{
-    awk -f "$SCRIPT_DIR/xctool.awk" 2>&1 >/dev/null
-}
-
-build_scheme ()
-{
-    local scheme=$1
-
-    echo "*** Cleaning $scheme..."
-    run_xctool -scheme "$scheme" clean >/dev/null || exit $?
-
-    echo "*** Building and testing $scheme..."
-    echo
-
-    local sdkflag=
-    local action=test
-
-    # Determine whether we can run unit tests for this target.
-    run_xctool -scheme "$scheme" run-tests | parse_build
-
-    local awkstatus=$?
-
-    if [ "$awkstatus" -eq "1" ]
-    then
-        # SDK not found, try for iphonesimulator.
-        sdkflag="-sdk iphonesimulator"
-
-        # Determine whether the unit tests will run with iphonesimulator
-        run_xctool $sdkflag -scheme "$scheme" run-tests | parse_build
-
-        awkstatus=$?
-
-        if [ "$awkstatus" -ne "0" ]
-        then
-            # Unit tests will not run on iphonesimulator.
-            sdkflag=""
-        fi
-    fi
-
-    if [ "$awkstatus" -ne "0" ]
-    then
-        # Unit tests aren't supported.
-        action=build
-    fi
-
-    run_xctool $sdkflag -scheme "$scheme" $action
-}
-
-export -f build_scheme
-export -f run_xctool
-export -f parse_build
-
-main

script/schemes.awk

@@ -1,10 +0,0 @@
-BEGIN {
-    FS = "\n";
-}
-
-/Schemes:/ {
-    while (getline && $0 != "") {
-        sub(/^ +/, "");
-        print "'" $0 "'";
-    }
-}

script/xctool.awk

@@ -1,25 +0,0 @@
-# Exit statuses:
-#
-# 0 - No errors found.
-# 1 - Wrong SDK. Retry with SDK `iphonesimulator`.
-# 2 - Missing target.
-
-BEGIN {
-    status = 0;
-}
-
-{
-    print;
-}
-
-/Testing with the '(.+)' SDK is not yet supported/ {
-    status = 1;
-}
-
-/does not contain a target named/ {
-    status = 2;
-}
-
-END {
-    exit status;
-}