swift初学之项目启动

 varwindow:UIWindow?

    funcapplication(_application:UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey:Any]?) ->Bool{

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

        letvc =ViewController()

        letnavVC =UINavigationController(rootViewController: vc)

        window?.rootViewController = navVC

        window?.makeKeyAndVisible(）

        return true

    }