PFFacebookUtils.logInInBackground不执行segue

Question

嗨，下面的代码不知何故不适用于segue。它返回：

警告:尝试显示其视图不在窗口层次结构中！

代码在IBAction按钮中运行。然后，我在没有PFFacebookUtils代码的情况下执行segue，它工作得很好。由此，我猜不能从PFFacebookUtils调用segue，因为它在后台某种程度上起作用。

代码：

PFFacebookUtils.logInInBackground(withReadPermissions: permissions) {
            (user: PFUser?, error: Error?) -> Void in
            if let user = user {
                if user.isNew {
                    print("User signed up and logged in through Facebook!")
                    self.performSegue(withIdentifier: "segueSignUpWindow", sender: nil)

                } else {
                    print("User logged in through Facebook!")
                    self.performSegue(withIdentifier: "segueSignUpWindow", sender: self)
            } else {
                print("Uh oh. The user cancelled the Facebook login.")
                self.loginCancelledLabel.alpha = 1
            }
        }

我尝试插入其他代码，例如：

DispatchQueue.main.async {
                let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
                let vc = storyboard.instantiateViewController(withIdentifier: "SignUp")
                self.show(vc, sender: self)
                print("Hello")

或具有职能：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if (segue.identifier == "segueSignUpWindow") {
            DispatchQueue.main.async {
                let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
                let vc = storyboard.instantiateViewController(withIdentifier: "SignUp")
                self.show(vc, sender: self)
                print("Hello")
            }
        }

毫无办法。有人有可行的解决方案吗？我的目标是使另一个故事板在登录或登录后继续。

我已经在堆栈溢出中查找了大多数线程。没有找到有效的解决办法。

Answer 1

我能得到的最接近的：

生成触发器var segueLogin : Bool = false (初始化值)。

当PFFacebookUtils获得segue所需的值时，将触发器更改为true：

PFFacebookUtils.logInInBackground(withReadPermissions: permissions) {
            (user: PFUser?, error: Error?) -> Void in
            if let user = user {
                if user.isNew {
                    print("User signed up and logged in through Facebook!")
                    self.segueLogin = true

                } else {
                    print("User logged in through Facebook!")
                    self.segueLogin = true
                }
            } else {
                print("Uh oh. The user cancelled the Facebook login.")
                self.loginCancelledLabel.alpha = 1
            }
        }

然后向viewDidAppear类添加代码。意识到每次PFFacebookUtils完成的时候都会启动。因此，它检查返回的值是否为真，并在成功的PFFacebookUtils会话之后执行segue：

override func viewDidAppear(_ animated: Bool) {
        if segueLogin == true {
            self.performSegue(withIdentifier: "segueSingup", sender: self)
        }
    }