AppDelegate.swift

//..
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        
        //Manually create the application window
        window = UIWindow(frame: UIScreen.main.bounds)
        
        //Custom theming on the application
        UIApplication.shared.statusBarStyle = .lightContent
        application.isStatusBarHidden = false
        UINavigationBar.appearance().isTranslucent = false
        UINavigationBar.appearance().tintColor = .white
        
        //Instantiate a navigation controller (nav1) and assign the randomly generated ViewController to it
        let nav1 = UINavigationController()
        nav1.navigationBar.isTranslucent = false
        nav1.navigationBar.barTintColor = .darkGray
        let vc = ViewController()
        nav1.viewControllers = [vc]
        
        //Set nav1 as the window's root viewcontroller
        window?.rootViewController = nav1
        
        //Show the window
        window?.makeKeyAndVisible()
        return true
    }