@synthesize window = _window;

@synthesize rootViewController = _rootViewController;

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

{

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

    _rootViewController = [[ViewController alloc] init];

    UINavigationController *rootNaviController = [[UINavigationController alloc] initWithRootViewController:_rootViewController];

    self.window.rootViewController = rootNaviController;

    [self.window makeKeyAndVisible];

    return YES;

}

UINavigationController *nav = (UINavigationController*)self.window.rootViewController;

            [nav pushViewController:controller animated:YES];