AppDelegate.m

@implementation MyAppDelegate

- (void) setUpDataMappingForObjectManager: (RKObjectManager*) objectManager
{
  // Workouts
  RKManagedObjectMapping* workoutMapping = [RKManagedObjectMapping mappingForClass: [Workout class]];
  
  workoutMapping.primaryKeyAttribute = @"workoutID";
  
  [workoutMapping mapKeyPath: @"id"           toAttribute: @"workoutID"];
  [workoutMapping mapKeyPath: @"name"         toAttribute: @"name"];
  [workoutMapping mapKeyPath: @"description"  toAttribute: @"workoutDescription"];
  [workoutMapping mapKeyPath: @"activities" toAttribute: @"activities"];
  
  [objectManager.mappingProvider setMapping: workoutMapping forKeyPath: @"workout"];
  
  
  // Activities
  RKManagedObjectMapping* activityMapping = [RKManagedObjectMapping mappingForClass: [Activity class]];
  
  activityMapping.primaryKeyAttribute = @"activityID";
  
  [activityMapping mapKeyPath: @"id" toAttribute: @"activityID"];
  [activityMapping mapKeyPath: @"name" toAttribute: @"name"];
  [activityMapping mapKeyPath: @"description" toAttribute: @"activityDescription"];
  [activityMapping mapRelationship: @"workout" withMapping: workoutMapping];
  
  [objectManager.mappingProvider setMapping: activityMapping forKeyPath: @"activity"];
}


- (BOOL) application: (UIApplication *) application didFinishLaunchingWithOptions: (NSDictionary *) launchOptions
{
  
  // View initialization stuff...

  RKObjectManager* objectManager = [RKObjectManager objectManagerWithBaseURL: @"http://localhost:3000"];
  objectManager.client.username = [userSettings stringForKey: @"email_address_preference"];
  objectManager.client.password = [userSettings stringForKey: @"password_preference"];
  
  // Enable automatic network activity indicator management
  objectManager.client.requestQueue.showsNetworkActivityIndicatorWhenBusy = YES;
    
  objectManager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename: @"MyRestKitApp.sqlite"
                                                           usingSeedDatabaseName: nil
                                                              managedObjectModel: nil
                                                                        delegate: self];
  
  
  [self setUpDataMappingForObjectManager: objectManager];

  [userSettings release];
  return YES;
}

@end

workouts.json

[
    {
        "created_at":"2011-08-06T20:47:37Z",
        "description":"Bacon ipsum dolor sit amet boudin pork chop ball tip, t-bone bresaola tongue jowl meatball meatloaf. T-bone shank brisket ground round flank beef, venison pork loin tri-tip pancetta pig shor.",
        "id":32,
        "name":"Workout Foo",
        "updated_at":"2011-08-06T20:47:37Z",
        "activities": [
            {
                "name":"Squats",
                "description":"Bacon ipsum dolor sit amet boudin pork chop ball tip, t-bone bresaola tongue jowl meat.",
                "duration":1872
            },
            {
                "name":"Pushups",
                "description":"Bacon ipsum dolor sit amet boudin pork chop ball tip, t-bone bresaola tongue jowl meatball meatloaf..",
                "count":139
            },
            {
                "name":"Pullups",
                "description":"Bacon ipsum dolor sit amet boudin pork chop ball tip, t-bone bresaola tongue jowl meatball meatloaf. T-bone shank brisket ground.",
                "duration":402,
                "count":61
            }
        ]
    }
]

WorkoutsTableViewController.m

@implementation WorkoutsTableViewController

@synthesize workouts;

- (void) loadObjectsFromDataStore
{
  NSDate* lastUpdatedAt = [[NSUserDefaults standardUserDefaults] objectForKey: @"last_updated_workouts_at"];
  NSDate* oneHourAgo = [[NSDate alloc] initWithTimeIntervalSinceNow: -3600];
  
  if ( lastUpdatedAt == nil || [lastUpdatedAt compare: oneHourAgo] == NSOrderedAscending ) {
    [self loadDataFromWebService];
  } else {
    [workouts release];
    
    NSFetchRequest* request = [Workout fetchRequest];
    NSSortDescriptor* descriptor = [NSSortDescriptor sortDescriptorWithKey: @"name"
                                                                 ascending: YES];
    [request setSortDescriptors: [NSArray arrayWithObject: descriptor]];
    
    workouts = [[Workout objectsWithFetchRequest: request] retain];
  }
  
  [oneHourAgo release];
}

- (void) loadDataFromWebService
{
  // Load the object model via RestKit	
  RKObjectManager* objectManager = [RKObjectManager sharedManager];
  
  [objectManager loadObjectsAtResourcePath: @"/workouts.json"
                                  delegate: self
                                     block: ^(RKObjectLoader* loader) {
                                       // Workouts are returned as a naked array in JSON, so we instruct the loader
                                       // to user the appropriate object mapping
                                       loader.objectMapping = [objectManager.mappingProvider objectMappingForClass: [Workout class]];
                                     }];
}


#pragma mark View Lifecycle Methods

- (void) viewDidAppear: (BOOL) animated
{
  [super viewDidAppear: animated];
  [self loadObjectsFromDataStore];
}


#pragma mark RestKit Object Loader Delegate Methods

- (void) objectLoader: (RKObjectLoader *) objectLoader
     didFailWithError: (NSError *) error
{
  UIAlertView* alert = [[[UIAlertView alloc] initWithTitle: @"Error" 
                                                   message: [error localizedDescription] 
                                                  delegate: nil 
                                         cancelButtonTitle: @"OK"
                                         otherButtonTitles: nil] autorelease];
  [alert show];
}

- (void) objectLoader: (RKObjectLoader*) objectLoader
       didLoadObjects: (NSArray*) objects
{
  [[NSUserDefaults standardUserDefaults] setObject: [NSDate date] forKey: @"last_updated_workouts_at"];
  [[NSUserDefaults standardUserDefaults] synchronize];
  
  [self loadObjectsFromDataStore];
  
  [workoutsTableView reloadData];
}

@end