Swift 在AppDelegate中执行segue

当Firebase令牌无效时，我希望将用户重定向到我的应用程序loginVC。这是我的代码：

func userErrorLogout() {

    print("user error logout")

    let storyboard = UIStoryboard(name: "Main", bundle: nil);
    let viewController: ViewController = storyboard.instantiateViewController(withIdentifier: "loginVC") as! ViewController;

    let rootViewController = self.window!.rootViewController as! UINavigationController;
    rootViewController.pushViewController(viewController, animated: true);
}

我在“let rootViewController:…=2019-11-27 13:03:49.364864+0100 Geo[25133:2193886]上收到一个错误致命错误：在展开可选值：file时意外发现nil

---

由于SWIFT对我来说是新手，我无法调试此消息。如何执行重定向？

您需要为您的rootViewController分配值。请尝试以下操作：

func userErrorLogout() {

print("user error logout")

let storyboard = UIStoryboard(name: "Main", bundle: nil);
let viewController: ViewController = storyboard.instantiateViewController(withIdentifier: "loginVC") as! ViewController;
let nav = UINavigationController(rootViewController: viewController)
self.window?.rootViewController = nav

---

}您需要使用以下代码：

let storyboard = UIStoryboard(name: "Main", bundle: nil);
let viewController: ViewController = storyboard.instantiateViewController(withIdentifier: "loginVC") as! ViewController;


let window = (UIApplication.shared.delegate as! AppDelegate).window!

DispatchQueue.main.async {
        window.rootViewController = viewController
}

---

你需要将viewcontroller设置为window。你可以像下面这样做。这段代码还有过渡动画，它提供淡入过渡的效果

    // MARK: WINDOW SET
func gotoIntro() {
    UIView.transition(with: window!, duration: 0.5, options: .transitionCrossDissolve, animations: {
        UIView.performWithoutAnimation({
            let introStoryboard = UIStoryboard(name: "Intro", bundle: nil)

            let navigationController = introStoryboard.instantiateInitialViewController() as! UINavigationController

            self.window?.rootViewController = navigationController
        })
    }, completion: nil)
}

---

从iOS 13开始，AppDelegate不再能够在启动开始时推送VC（不是100%确定）

如果希望从根目录显示视图，则必须使用SceneDelegate。 要做到这一点，只需在ScenedLegate文件中执行即可。我已经在自己的应用程序上测试了这种方法，并且100%有效

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        guard let windowScene = (scene as? UIWindowScene) else { return }

        self.window = UIWindow(windowScene: windowScene)
        // check if the token is valid
        if valid  {
            let vc = UIStoryboard.init(name: "Main", bundle: Bundle.main).instantiateViewController(withIdentifier: "yourVC")
            self.window?.rootViewController = vc
            self.window?.makeKeyAndVisible()
        }
        else {
            // token is invalid
            let storyboard = UIStoryboard(name: "Main", bundle: nil)
            let rootVC = storyboard.instantiateViewController(identifier: "invalidVC")
            let rootNC = UINavigationController(rootViewController: rootVC)
            self.window?.rootViewController = rootNC
            self.window?.makeKeyAndVisible()
        }
    }

---

确保您的

self.window！.rootViewController

是

UINavigationController

。进入情节提要并将初始ViewController添加为

UINavigationController