I can't push the loginViewcontroller with navigationController on self.window

Question

I have point a pageViewController as the rootViewController,and then I wanna display a login view above the pageViewController if not sign in.

NLLoginViewController *loginVC = [[NLLoginViewController alloc]init];
UINavigationController *navigation = [[UINavigationController alloc]initWithRootViewController:loginVC];
[self.window addSubview:navigation.view];

Answer 1

You should do the following thing

self.window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen] bounds]];
NLLoginViewController *loginVC = [[NLLoginViewController alloc]initWithNibName:@"NLLoginViewController" bundle:nil];
PageViewController *pageVC = [[PageViewController alloc]initWithNibName:@"PageViewController" bundle:nil];
UINavigationController *navigation
if(![[NSUserDefaults standardUserDefaults] boolForKey:@"is_SignedIn"]))
  navigation = [[UINavigationController alloc]initWithRootViewController:logindVC];
else
   navigation = [[UINavigationController alloc]initWithRootViewController:pageVC];
self.window.rootViewController = navigation;

After that In login view controller, you have to set

[[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"is_SignedIn"];