Extract the MTLModel protocol

Mantle/MTLJSONAdapter.h

@@ -8,10 +8,10 @@
 
 #import <Foundation/Foundation.h>
 
-@class MTLModel;
+@protocol MTLModel;
 
 // A MTLModel object that supports being parsed from and serialized to JSON.
-@protocol MTLJSONSerializing
+@protocol MTLJSONSerializing <MTLModel>
 @required
 
 // Specifies how to map property keys to different key paths in JSON.
@@ -66,7 +66,7 @@ extern const NSInteger MTLJSONAdapterErrorInvalidJSONDictionary;
 
 // 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;
+@property (nonatomic, strong, readonly) id<MTLJSONSerializing> model;
 
 // Attempts to parse a JSON dictionary into a model object.
 //
@@ -91,7 +91,7 @@ extern const NSInteger MTLJSONAdapterErrorInvalidJSONDictionary;
 //         serializing.
 //
 // Returns a JSON dictionary, or nil if a serialization error occurred.
-+ (NSDictionary *)JSONDictionaryFromModel:(MTLModel<MTLJSONSerializing> *)model error:(NSError **)error;
++ (NSDictionary *)JSONDictionaryFromModel:(id<MTLJSONSerializing>)model error:(NSError **)error;
 
 // Initializes the receiver by attempting to parse a JSON dictionary into
 // a model object.
@@ -114,7 +114,7 @@ extern const NSInteger MTLJSONAdapterErrorInvalidJSONDictionary;
 //
 // model - The model to use for JSON serialization. This argument must not be
 //         nil.
-- (id)initWithModel:(MTLModel<MTLJSONSerializing> *)model;
+- (id)initWithModel:(id<MTLJSONSerializing>)model;
 
 // Serializes the receiver's `model` into JSON.
 //
@@ -176,6 +176,8 @@ extern const NSInteger MTLJSONAdapterErrorInvalidJSONDictionary;
 
 @end
 
+@class MTLModel;
+
 @interface MTLJSONAdapter (Deprecated)
 
 + (NSDictionary *)JSONDictionaryFromModel:(MTLModel<MTLJSONSerializing> *)model __attribute__((deprecated("Replaced by +JSONDictionaryFromModel:error:")));

Mantle/MTLJSONAdapter.m

@@ -59,7 +59,7 @@ + (id)modelOfClass:(Class)modelClass fromJSONDictionary:(NSDictionary *)JSONDict
 	return adapter.model;
 }
 
-+ (NSDictionary *)JSONDictionaryFromModel:(MTLModel<MTLJSONSerializing> *)model error:(NSError **)error {
++ (NSDictionary *)JSONDictionaryFromModel:(id<MTLJSONSerializing>)model error:(NSError **)error {
 	MTLJSONAdapter *adapter = [[self alloc] initWithModel:model];
 
 	return [adapter serializeToJSONDictionary:error];
@@ -74,7 +74,6 @@ - (id)init {
 
 - (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)modelClass error:(NSError **)error {
 	NSParameterAssert(modelClass != nil);
-	NSParameterAssert([modelClass isSubclassOfClass:MTLModel.class]);
 	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)]);
 
 	if (JSONDictionary == nil || ![JSONDictionary isKindOfClass:NSDictionary.class]) {
@@ -103,7 +102,6 @@ - (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)mo
 			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);
 	}
 
@@ -190,7 +188,7 @@ - (id)initWithJSONDictionary:(NSDictionary *)JSONDictionary modelClass:(Class)mo
 	return self;
 }
 
-- (id)initWithModel:(MTLModel<MTLJSONSerializing> *)model {
+- (id)initWithModel:(id<MTLJSONSerializing>)model {
 	NSParameterAssert(model != nil);
 
 	self = [super init];
@@ -272,7 +270,6 @@ - (NSString *)JSONKeyPathForPropertyKey:(NSString *)key {
 
 - (NSDictionary *)valueTransformersForModelClass:(Class)modelClass {
 	NSParameterAssert(modelClass != nil);
-	NSParameterAssert([modelClass isSubclassOfClass:MTLModel.class]);
 	NSParameterAssert([modelClass conformsToProtocol:@protocol(MTLJSONSerializing)]);
 
 	NSMutableDictionary *result = [NSMutableDictionary dictionary];

Mantle/MTLManagedObjectAdapter.h

@@ -8,11 +8,11 @@
 
 #import <CoreData/CoreData.h>
 
-@class MTLModel;
+@protocol MTLModel;
 
 // A MTLModel object that supports being serialized to and from Core Data as an
 // NSManagedObject.
-@protocol MTLManagedObjectSerializing
+@protocol MTLManagedObjectSerializing <MTLModel>
 @required
 
 // The name of the Core Data entity that the receiver serializes to and
@@ -171,7 +171,7 @@ extern const NSInteger MTLManagedObjectAdapterErrorUnsupportedRelationshipClass;
 //           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;
++ (id)managedObjectFromModel:(id<MTLManagedObjectSerializing>)model insertingIntoContext:(NSManagedObjectContext *)context error:(NSError **)error;
 
 // An optional value transformer that should be used for properties of the given
 // class.

Mantle/MTLManagedObjectAdapter.m

@@ -82,15 +82,15 @@ + (id)modelOfClass:(Class)modelClass fromManagedObject:(NSManagedObject *)manage
 // 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;
+- (id)managedObjectFromModel:(id<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;
++ (id)managedObjectFromModel:(id<MTLManagedObjectSerializing>)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error;
 
 // Looks at propertyKeysForManagedObjectUniquing and forms an NSPredicate
 // using the uniquing keys and the provided model.
@@ -104,7 +104,7 @@ + (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model inse
 // Returns a predicate, or nil if no predicate is needed or if an error
 // occurred. Clients should inspect the success parameter to decide how to
 // proceed with the result.
-- (NSPredicate *)uniquingPredicateForModel:(MTLModel<MTLManagedObjectSerializing> *)model success:(BOOL *)success error:(NSError **)error;
+- (NSPredicate *)uniquingPredicateForModel:(id<MTLManagedObjectSerializing>)model success:(BOOL *)success error:(NSError **)error;
 
 @end
 
@@ -146,7 +146,7 @@ - (id)modelFromManagedObject:(NSManagedObject *)managedObject processedObjects:(
 	NSManagedObjectContext *context = managedObject.managedObjectContext;
 
 	NSDictionary *managedObjectProperties = entity.propertiesByName;
-	MTLModel *model = [[self.modelClass alloc] init];
+	NSObject<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.
@@ -199,7 +199,7 @@ - (id)modelFromManagedObject:(NSManagedObject *)managedObject processedObjects:(
 					NSMutableArray *models = [NSMutableArray arrayWithCapacity:[relationshipCollection count]];
 
 					for (NSManagedObject *nestedObject in relationshipCollection) {
-						MTLModel *model = [self.class modelOfClass:nestedClass fromManagedObject:nestedObject processedObjects:processedObjects error:error];
+						id<MTLManagedObjectSerializing> model = [self.class modelOfClass:nestedClass fromManagedObject:nestedObject processedObjects:processedObjects error:error];
 						if (model == nil) return nil;
 
 						[models addObject:model];
@@ -219,7 +219,7 @@ - (id)modelFromManagedObject:(NSManagedObject *)managedObject processedObjects:(
 
 				if (nestedObject == nil) return YES;
 
-				MTLModel *model = [self.class modelOfClass:nestedClass fromManagedObject:nestedObject processedObjects:processedObjects error:error];
+				id<MTLManagedObjectSerializing> model = [self.class modelOfClass:nestedClass fromManagedObject:nestedObject processedObjects:processedObjects error:error];
 				if (model == nil) return NO;
 
 				return setValueForKey(propertyKey, model);
@@ -312,7 +312,7 @@ + (id)modelOfClass:(Class)modelClass fromManagedObject:(NSManagedObject *)manage
 	return [adapter modelFromManagedObject:managedObject processedObjects:processedObjects error:error];
 }
 
-- (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
+- (id)managedObjectFromModel:(id<MTLManagedObjectSerializing>)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
 	NSParameterAssert(model != nil);
 	NSParameterAssert(context != nil);
 	NSParameterAssert(processedObjects != nil);
@@ -431,7 +431,7 @@ - (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model inse
 		};
 
 		NSManagedObject * (^objectForRelationshipFromModel)(id) = ^ id (id model) {
-			if (![model isKindOfClass:MTLModel.class] || ![model conformsToProtocol:@protocol(MTLManagedObjectSerializing)]) {
+			if (![model conformsToProtocol:@protocol(MTLManagedObjectSerializing)]) {
 				NSString *failureReason = [NSString stringWithFormat:NSLocalizedString(@"Property of class %@ cannot be encoded into an NSManagedObject.", @""), [model class]];
 
 				NSDictionary *userInfo = @{
@@ -471,7 +471,7 @@ - (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model inse
 					relationshipCollection = [NSMutableSet set];
 				}
 
-				for (MTLModel *model in value) {
+				for (id<MTLModel> model in value) {
 					NSManagedObject *nestedObject = objectForRelationshipFromModel(model);
 					if (nestedObject == nil) return NO;
 
@@ -548,7 +548,7 @@ - (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model inse
 	return managedObject;
 }
 
-+ (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context error:(NSError **)error {
++ (id)managedObjectFromModel:(id<MTLManagedObjectSerializing>)model insertingIntoContext:(NSManagedObjectContext *)context error:(NSError **)error {
 	CFDictionaryKeyCallBacks keyCallbacks = kCFTypeDictionaryKeyCallBacks;
 
 	// Compare MTLModel keys using pointer equality, not -isEqual:.
@@ -564,7 +564,7 @@ + (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model inse
 	return [self managedObjectFromModel:model insertingIntoContext:context processedObjects:processedObjects error:error];
 }
 
-+ (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
++ (id)managedObjectFromModel:(id<MTLManagedObjectSerializing>)model insertingIntoContext:(NSManagedObjectContext *)context processedObjects:(CFMutableDictionaryRef)processedObjects error:(NSError **)error {
 	NSParameterAssert(model != nil);
 	NSParameterAssert(context != nil);
 	NSParameterAssert(processedObjects != nil);
@@ -578,7 +578,29 @@ + (id)managedObjectFromModel:(MTLModel<MTLManagedObjectSerializing> *)model inse
 	return [adapter managedObjectFromModel:model insertingIntoContext:context processedObjects:processedObjects error:error];
 }
 
-- (NSPredicate *)uniquingPredicateForModel:(MTLModel<MTLManagedObjectSerializing> *)model success:(BOOL *)success error:(NSError **)error {
+- (NSValueTransformer *)entityAttributeTransformerForKey:(NSString *)key {
+	NSParameterAssert(key != nil);
+
+	SEL selector = MTLSelectorWithKeyPattern(key, "EntityAttributeTransformer");
+	if ([self.modelClass respondsToSelector:selector]) {
+		NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[self.modelClass methodSignatureForSelector:selector]];
+		invocation.target = self.modelClass;
+		invocation.selector = selector;
+		[invocation invoke];
+
+		__unsafe_unretained id result = nil;
+		[invocation getReturnValue:&result];
+		return result;
+	}
+
+	if ([self.modelClass respondsToSelector:@selector(entityAttributeTransformerForKey:)]) {
+		return [self.modelClass entityAttributeTransformerForKey:key];
+	}
+
+	return nil;
+}
+
+- (NSPredicate *)uniquingPredicateForModel:(NSObject<MTLManagedObjectSerializing> *)model success:(BOOL *)success error:(NSError **)error {
 	if (![self.modelClass respondsToSelector:@selector(propertyKeysForManagedObjectUniquing)]) return nil;
 
 	NSSet *propertyKeys = [self.modelClass propertyKeysForManagedObjectUniquing];

Mantle/MTLModel+NSCoding.m

@@ -10,7 +10,6 @@
 #import "EXTRuntimeExtensions.h"
 #import "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

@@ -21,26 +21,42 @@
 //                                (like `NSCoding`) and equality, since it can
 //                                be expected to stick around.
 typedef enum : NSUInteger {
-	MTLPropertyStorageNone,
-	MTLPropertyStorageTransitory,
-	MTLPropertyStoragePermanent,
+    MTLPropertyStorageNone,
+    MTLPropertyStorageTransitory,
+    MTLPropertyStoragePermanent,
 } MTLPropertyStorage;
 
-// An abstract base class for model objects, using reflection to provide
-// sensible default behaviors.
+// This protocol defines the minimal interface that classes need to implement to
+// interact with Mantle adapters.
 //
-// The default implementations of <NSCopying>, -hash, and -isEqual: make use of
-// the +propertyKeys method.
-@interface MTLModel : NSObject <NSCopying>
+// 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>
 
-// Returns a new instance of the receiver initialized using
-// -initWithDictionary:error:.
+// 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.
+// A dictionary representing the properties of the receiver.
 //
-// This is the designated initializer for this class.
-- (instancetype)init;
+// 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;
 
 // Initializes the receiver using key-value coding, setting the keys and values
 // in the given dictionary.
@@ -56,31 +72,52 @@ typedef enum : NSUInteger {
 // Returns an initialized model object, or nil if validation failed.
 - (instancetype)initWithDictionary:(NSDictionary *)dictionaryValue error:(NSError **)error;
 
+// 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;
+
 // 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.
+@end
+
+// An abstract base class for model objects, using reflection to provide
+// sensible default behaviors.
 //
-// The default implementation combines the values corresponding to all
-// +propertyKeys into a dictionary, with any nil values represented by NSNull.
+// The default implementations of <NSCopying>, -hash, and -isEqual: make use of
+// the +propertyKeys method.
+@interface MTLModel : NSObject <MTLModel>
+
+// Initializes the receiver using key-value coding, setting the keys and values
+// in the given dictionary.
 //
-// This property must never be nil.
-@property (nonatomic, copy, readonly) NSDictionary *dictionaryValue;
+// 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 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.
+// Initializes the receiver with default values.
 //
+// This is the designated initializer for this class.
+- (instancetype)init;
+
 // 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;
+- (void)mergeValueForKey:(NSString *)key fromModel:(id<MTLModel>)model;
 
 // 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;
+- (void)mergeValuesForKeysFromModel:(id<MTLModel>)model;
 
 // The storage behavior of a given key.
 //

Mantle/MTLModel.m

@@ -240,7 +240,7 @@ + (MTLPropertyStorage)storageBehaviorForPropertyWithKey:(NSString *)propertyKey
 
 #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:");
@@ -260,7 +260,7 @@ - (void)mergeValueForKey:(NSString *)key fromModel:(MTLModel *)model {
 	[invocation invoke];
 }
 
-- (void)mergeValuesForKeysFromModel:(MTLModel *)model {
+- (void)mergeValuesForKeysFromModel:(id<MTLModel>)model {
 	for (NSString *key in self.class.propertyKeys) {
 		[self mergeValueForKey:key fromModel:model];
 	}