How to set root view controller

Question

I set up an empty app with only an app delegate class, then subclassed a view controller class to create a xib to layout the app and make connections.

But when I tried

Answer 1

You need to set 2 things for that..

1. in AppDelegate.m file: _applicationDidFinishLaunchingWithOptions_

   self.window.rootViewController = self.viewController;

2. in application.m

   retVal = UIApplicationMain(argc, argv, nil, @"AppDelegate");

Answer 2

Since you're apparently using .xib files, load your view controller and the set the window's rootViewController property to your view controller in -application:didFinishLaunchingWithOptions:.

Answer 3

in AppDelegate.m

(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:UIScreen.mainScreen.bounds];



    UIViewController *viewController = // determine the initial view controller here and instantiate it with [storyboard instantiateViewControllerWithIdentifier:];

    self.window.rootViewController = viewController;//making a view to root view
    [self.window makeKeyAndVisible];

    return YES;
}

Answer 4

Applications are expected to have a root view controller

Replace in AppDelegate

 [window addSubview:[someController view]];

to

 [self.window setRootViewController:someController];