SWIFT 5
If you don't have a ViewController set as the initial ViewController in storyboard, you need to do 2 things:
Finally, you can now add your code in SceneDelegate:
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
// Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
// If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
// This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
guard let windowScene = (scene as? UIWindowScene) else { return }
window = UIWindow(windowScene: windowScene)
let storyboard = UIStoryboard(name: "Main", bundle: nil)
// Make sure you set an Storyboard ID for the view controller you want to instantiate
window?.rootViewController = storyboard.instantiateViewController(withIdentifier: identifier)
window?.makeKeyAndVisible()
}