AppDelegate.swift

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
      
      window = UIWindow(frame: UIScreen.main.bounds)
      self.window?.rootViewController = viewController()
      self.window?.makeKeyAndVisible()
        
        return true
    }