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

Examples/RKTwitterCoreData/Classes/RKTwitterAppDelegate.m

@@ -11,7 +11,6 @@
 #import "RKTwitterAppDelegate.h"
 #import "RKTwitterViewController.h"
 #import "RKTStatus.h"
-#import "RKTUser.h"
 
 @implementation RKTwitterAppDelegate
 
@@ -21,20 +20,52 @@
 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
     // Initialize RestKit
 	RKObjectManager* objectManager = [RKObjectManager objectManagerWithBaseURL:@"http://twitter.com"];
-	RKObjectMapper* mapper = objectManager.mapper;
     
     // Enable automatic network activity indicator management
     [RKRequestQueue sharedQueue].showsNetworkActivityIndicatorWhenBusy = YES;
     
-    // Update date format so that we can parse twitter dates properly
+    // Initialize object store
+    objectManager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:@"RKTwitterData.sqlite" usingSeedDatabaseName:RKDefaultSeedDatabaseFileName managedObjectModel:nil];
+    
+    // Setup our object mappings    
+    /*!
+     Mapping by entity. Here we are configuring a mapping by targetting a Core Data entity with a specific
+     name. This allows us to map back Twitter user objects directly onto NSManagedObject instances --
+     there is no backing model class!
+     */
+    RKManagedObjectMapping* userMapping = [RKManagedObjectMapping mappingForEntityWithName:@"RKTUser"];
+    userMapping.primaryKeyAttribute = @"userID";
+    [userMapping mapKeyPath:@"id" toAttribute:@"userID"];
+    [userMapping mapKeyPath:@"screen_name" toAttribute:@"screenName"];
+    [userMapping mapAttributes:@"name", nil];
+    
+    /*!
+     Map to a target object class -- just as you would for a non-persistent class. The entity is resolved
+     for you using the Active Record pattern where the class name corresponds to the entity name within Core Data.
+     Twitter status objects will be mapped onto RKTStatus instances.
+     */
+    RKManagedObjectMapping* statusMapping = [RKManagedObjectMapping mappingForClass:[RKTStatus class]];
+    statusMapping.primaryKeyAttribute = @"statusID";
+    [statusMapping mapKeyPathsToAttributes:@"id", @"statusID",
+     @"created_at", @"createdAt",
+     @"text", @"text",
+     @"url", @"urlString",
+     @"in_reply_to_screen_name", @"inReplyToScreenName",
+     @"favorited", @"isFavorited", 
+     nil];
+    [statusMapping mapRelationship:@"user" withObjectMapping:userMapping];
+    
+    // Update date format so that we can parse Twitter dates properly
 	// Wed Sep 29 15:31:08 +0000 2010
-	NSMutableArray* dateFormats = [[[mapper dateFormats] mutableCopy] autorelease];
-	[dateFormats addObject:@"E MMM d HH:mm:ss Z y"];
-	[mapper setDateFormats:dateFormats];
-	
-	// Add our element to object mappings
-	[mapper registerClass:[RKTUser class] forElementNamed:@"user"];
-	[mapper registerClass:[RKTStatus class] forElementNamed:@"status"];
+	[statusMapping.dateFormatStrings addObject:@"E MMM d HH:mm:ss Z y"];
+    
+    // Register our mappings with the provider
+    [objectManager.mappingProvider setMapping:userMapping forKeyPath:@"user"];
+    [objectManager.mappingProvider setMapping:statusMapping forKeyPath:@"status"];
+    
+    // Uncomment this to use XML, comment it to use JSON
+    //  objectManager.acceptMIMEType = RKMIMETypeXML;
+    //  [objectManager.mappingProvider setMapping:statusMapping forKeyPath:@"statuses.status"];
     
     // Database seeding is configured as a copied target of the main application. There are only two differences
     // between the main application target and the 'Generate Seed Database' target:
@@ -46,7 +77,7 @@
     RKManagedObjectSeeder* seeder = [RKManagedObjectSeeder objectSeederWithObjectManager:objectManager];
     
     // Seed the database with instances of RKTStatus from a snapshot of the RestKit Twitter timeline
-    [seeder seedObjectsFromFile:@"restkit.json" toClass:[RKTStatus class] keyPath:nil];
+    [seeder seedObjectsFromFile:@"restkit.json" withObjectMapping:statusMapping];
     
     // Seed the database with RKTUser objects. The class will be inferred via element registration
     [seeder seedObjectsFromFiles:@"users.json", nil];
@@ -54,13 +85,10 @@
     // Finalize the seeding operation and output a helpful informational message
     [seeder finalizeSeedingAndExit];
     
-    // NOTE: If all of your mapped objects use element -> class registration, you can perform seeding in one line of code:
+    // NOTE: If all of your mapped objects use keyPath -> objectMapping registration, you can perform seeding in one line of code:
     // [RKManagedObjectSeeder generateSeedDatabaseWithObjectManager:objectManager fromFiles:@"users.json", nil];
 #endif
     
-    // Initialize object store
-    objectManager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:@"RKTwitterData.sqlite" usingSeedDatabaseName:RKDefaultSeedDatabaseFileName managedObjectModel:nil];
-    
     // Create Window and View Controllers
 	RKTwitterViewController* viewController = [[[RKTwitterViewController alloc] initWithNibName:nil bundle:nil] autorelease];
 	UINavigationController* controller = [[UINavigationController alloc] initWithRootViewController:viewController];