ios - 从 'BaseViewController' 到 'FUIAuthDelegate' 的条件转换始终成功

Question

请注意，我是 Xcode10.1 的新手。

我已经在 Xcode 中对我的移动应用实现了 Firebase 身份验证；登录有效，但我收到一条错误消息

Conditional cast from 'BaseViewController' to 'FUIAuthDelegate' always succeeds

我看到的症状是登录屏幕只会在我完全关闭 Xcode 并重新启动应用程序时出现。

无法在网络上找到任何对此错误的引用

class BaseViewController: UIViewController, SlideMenuDelegate, FUIAuthDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()
        addSlideMenuButton()
        // Do any additional setup after loading the view.
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        if Auth.auth().currentUser != nil {
        } 
        else {
            let authUI = FUIAuth.defaultAuthUI()
            authUI?.delegate = self as? FUIAuthDelegate ***this is where im receiving the error***

            let providers: [FUIAuthProvider] = [
                FUIGoogleAuth()]

            authUI?.providers = providers
            let authViewController = authUI!.authViewController()
            self.present(authViewController, animated: true, completion: nil)
        }
    }
}

Answer 1

首先，错误是警告(黄色)。

如果一个类/结构采用一个协议(protocol)，它成为编译器方面的协议(protocol)，所以 BaseViewController 是 FUIAuthDelegate.

条件转换是多余的，这就是警告告诉您的内容。

let authUI = FUIAuth.defaultAuthUI()!
authUI.delegate = self