gistfile1.m

//Create store and moc:
   NSURL *baseURL = [NSURL URLWithString:myUrl];
    RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:baseURL];

 //not sure what this does but it's in example project
    NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
    RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel];
    objectManager.managedObjectStore = managedObjectStore;

NSString *modelPath = nil;
for (NSBundle* bundle in [NSBundle allBundles])
{
modelPath = [bundle pathForResource:@"MyApp" ofType:@"momd"];
if (modelPath)
break;
}

NSAssert(modelPath != nil, @"Could not find managed object model.");
mom = [[NSManagedObjectModel alloc] initWithContentsOfURL:[NSURL fileURLWithPath:modelPath]];

[managedObjectStore createPersistentStoreCoordinator];
    NSString *storePath = [RKApplicationDataDirectory() stringByAppendingPathComponent:@"MyApp.sqlite"];
    NSString *seedPath = [[NSBundle mainBundle] pathForResource:@"RKSeedDatabase" ofType:@"sqlite"];
    NSError *error;
    NSPersistentStore *persistentStore = [managedObjectStore addSQLitePersistentStoreAtPath:storePath fromSeedDatabaseAtPath:seedPath error:&error];
    NSAssert(persistentStore, @"Failed to add persistent store with error: %@", error);

    // Create the managed object contexts
    [managedObjectStore createManagedObjectContexts];


    // Configure a managed object cache to ensure we do not create duplicate objects
    managedObjectStore.managedObjectCache = [[RKInMemoryManagedObjectCache alloc] initWithManagedObjectContext:managedObjectStore.mainQueueManagedObjectContext];


//Create mapping
RKEntityMapping * someMapping = [RKEntityMapping mappingForEntityForName:@"SomeClass" inManagedObjectStore:managedObjectStore];
[someMapping addAttributeMappingsFromDictionary:@{
     @"some_key" : @"someAttr"
];

//relationship mapping
	RKRelationshipMapping* relationShipMapping = [RKRelationshipMapping relationshipMappingFromKeyPath:@"child"
                                                                                             toKeyPath:@"child"
                                                                                           withMapping:childeMapping];
	[someMapping addPropertyMapping:relationShipMapping];


//To load objects use:
    [[RKObjectManager sharedManager] getObject:[[MyObject class] path:resourcePath parameters:nil success: error:];