NSBackboneViewController.mm

- (void)viewDidLoad
{
  [super viewDidLoad];
  [self observeModel]
  [self render];
}

- (void)observeModel
{
  // KVO is used to observe model changes
  __weak id weakSelf = self;
  [self.model addObserverForKeyPath:@"favorite" owner:self block:^(id observed, NSDictionary *change) {
    [weakSelf render];
  }];
}

- (void)favoriteButtonTapped:(id)sender
{
  // The action only changes the data, not the UI
  self.model.favorite = YES;
}

- (void)render
{
  self.label.text = (self.model.favorite ? @"Favorite" : @"Not favorite");
}

// Un-observing code is left out to simplify the example