AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

  self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

  // Override point for customization after application launch
  self.window.backgroundColor = [UIColor whiteColor];

  MainViewController *viewController = [[MainViewController alloc] init];

  self.window.rootViewController = viewController;
  
  [self.window makeKeyAndVisible];
 
  return YES;
}