Why window is nil in AppDelegate

Question

I need to present view controller from the AppDelegate, so I wrote the following code:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let authViewController = storyboard.instantiateViewControllerWithIdentifier("ViewController") as ViewController
if let keyWindow = UIApplication.sharedApplication().keyWindow {
    keyWindow.rootViewController = authViewController
}

Unfortunately, window and keyWindow are both nil. Why?

Solution

You need to create the window yourself in AppDelegate if not using the main interface option:

self.window = UIWindow(frame:UIScreen.mainScreen().bounds)

Swift 3.0+

self.window = UIWindow(frame: UIScreen.main.bounds)

Then call your code above, using window.

Finally, call makeKeyAndVisible() on the window.

Comments

[jrturton]

When is this code being executed?

[FrozenHeart]

@jrturton This is code is execute in the func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool function

[jrturton]

Ok, in that function your app won't have a window unless you've made one manually, or you've set a storyboard or xib as the launch interface. Have you done that?

[FrozenHeart]

@jrturton No. How can I do it via Interface Builder?

[FrozenHeart]

I don't want to automatically load the initial view controller, because I need to present either authorization view controller or the main view controller manually

[FrozenHeart]

Thanks for the answer! btw, window doesn't have makeKeyAndOrderFront function

[FrozenHeart]

It works as expected without makeKeyAndVisible function call too. Is it necessary?

[jrturton]

It was always there on the templates so I assumed so. Don't know.

[Mitesh Mewada]

for Swift 5 self.window = UIWindow(frame:UIScreen.main.bounds)