Application windows are expected to have a root view controller at the end of application launch warning

It’s odd to be setting your window’s rootViewController in application:didFinishLaunchingWithOptions: if you have a MainWindow.xib. Usually a project follows one of three templates:

• Some projects have a MainWindow.xib. The target’s “Main Interface” is set to “MainWindow” in the target’s Summary tab (or in its Info.plist). This xib’s File’s Owner is UIApplication. The xib contains an instance of AppDelegate, connected to the File’s Owner’s delegate outlet. The xib also contains a UIWindow, whose rootViewController outlet is connected to a UIViewController (or subclass, such as UINavigationController), which is also in the xib. By the time the application delegate receives the application:didFinishLaunchingWithOptions: message, the xib is entirely loaded, so the window and its root view controller are already set up.

• Other projects don’t have a MainWindow.xib. The target’s “Main Interface” is empty. Instead, the UIApplicationMain function creates an instance of AppDelegate, sets it as the UIApplication‘s delegate, and sends it the application:didFinishLaunchingWithOptions: message. The app delegate handles that message by creating a UIWindow, creating a view controller (or several), and setting the window’s rootViewController property. The default version looks like this:

  - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
  {
      self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
      // Override point for customization after application launch.
      self.viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
      self.window.rootViewController = self.viewController;
      [self.window makeKeyAndVisible];
      return YES;
  }
  

• Some projects have a MainStoryboard.storyboard. I’m not going to describe this in detail because it doesn’t seem relevant to your problem.

The problem you’re describing makes it sound like you’re using half of the first template, and half of the second template. That won’t work. You need to decide which approach you’re taking, and go all-in.