Implementation of Object Mapping 2.0 design:

* Removed RestKit from inheritance hierarchy
  * Mappings are implemented as concrete classes
  * Mapper is much more flexible & powerful
  * Much more robust error handling
  * Serialization is reimplemented as an object mapping operation
  * Added ability to serialize to JSON natively
  * Reworked Core Data integration
  * Simplified the codebase substantially

Code/ObjectMapping/RKObjectSerializer.m

@@ -0,0 +1,101 @@
+//
+//  RKObjectSerializer.m
+//  RestKit
+//
+//  Created by Blake Watters on 5/2/11.
+//  Copyright 2011 Two Toasters. All rights reserved.
+//
+
+#import "../Network/RKRequestSerialization.h"
+#import "../Support/RKMIMETypes.h"
+#import "../Support/RKParser.h"
+#import "RKObjectSerializer.h"
+#import "NSDictionary+RKRequestSerialization.h"
+#import "RKParserRegistry.h"
+#import "Logging.h"
+
+@implementation RKObjectSerializer
+
+@synthesize object = _object;
+@synthesize mapping = _mapping;
+
++ (id)serializerWithObject:(id)object mapping:(RKObjectMapping*)mapping {
+    return [[[self alloc] initWithObject:object mapping:mapping] autorelease];
+}
+
+- (id)initWithObject:(id)object mapping:(RKObjectMapping*)mapping {
+    self = [super init];
+    if (self) {
+        _object = [object retain];
+        _mapping = [mapping retain];
+    }
+    return self;
+}
+
+- (void)dealloc {
+    [_object release];
+    [_mapping release];
+    
+    [super dealloc];
+}
+
+- (id<RKRequestSerializable>)serializationForMIMEType:(NSString*)MIMEType error:(NSError**)error {
+    NSMutableDictionary* dictionary = [NSMutableDictionary dictionary];
+    RKObjectMappingOperation* operation = [RKObjectMappingOperation mappingOperationFromObject:_object toObject:dictionary withObjectMapping:_mapping];
+    operation.delegate = self;
+    operation.objectFactory = self;
+    BOOL success = [operation performMapping:error];
+    if (!success) {
+        return nil;
+    }
+    
+    // Optionally enclose the serialized object within a container...
+    if (_mapping.rootKeyPath) {
+        // TODO: Should log this...
+        dictionary = [NSMutableDictionary dictionaryWithObject:dictionary forKey:_mapping.rootKeyPath];
+    }
+    
+    if ([MIMEType isEqualToString:RKMIMETypeFormURLEncoded]) {
+        // Dictionaries are natively RKRequestSerializable as Form Encoded
+        return dictionary;
+    } else {
+        id<RKParser> parser = [[RKParserRegistry sharedRegistry] parserForMIMEType:MIMEType];
+        NSString* string = [parser stringFromObject:dictionary error:error];
+        if (string == nil) {
+            return nil;
+        }
+        
+        NSData* data = [string dataUsingEncoding:NSUTF8StringEncoding];
+        return [RKRequestSerialization serializationWithData:data MIMEType:MIMEType];
+    }
+    
+    return nil;
+}
+
+#pragma mark - RKObjectMappingOperationDelegate
+
+- (void)objectMappingOperation:(RKObjectMappingOperation *)operation didSetValue:(id)value forKeyPath:(NSString *)keyPath usingMapping:(RKObjectAttributeMapping *)mapping {
+    id transformedValue = nil;
+    
+    if ([value isKindOfClass:[NSDate class]]) {
+        // Date's are not natively serializable, must be encoded as a string
+        transformedValue = [value description];
+    } else if ([value isKindOfClass:[NSDecimalNumber class]]) {
+        // Precision numbers are serialized as strings to work around Javascript notation limits
+        transformedValue = [(NSDecimalNumber*)value stringValue];        
+    }
+    
+    if (transformedValue) {
+        RKLOG_MAPPING(RKLogLevelDebug, @"Serialized %@ value at keyPath to %@ (%@)", NSStringFromClass([value class]), NSStringFromClass([transformedValue class]), value);
+        [operation.destinationObject setValue:transformedValue forKey:keyPath];
+    }
+}
+
+#pragma mark - RKObjectFactory
+
+// We always serialize back to a dictionary
+- (id)objectWithMapping:(RKObjectMapping*)objectMapping andData:(id)mappableData {
+    return [NSMutableDictionary dictionary];
+}
+
+@end