ios - 当尝试注销/放松回到主屏幕时，如果甚至没有 optional ，为什么会收到“找到零”错误？

Question

错误所在行:

self.passwordField.delegate = self

按钮中的代码:

 @IBAction func unwindToRed(_ sender: Any) {

    do {
                   try Auth.auth().signOut()
                   let ViewController1 = ViewController()
                   let ViewNavigationController = UINavigationController(rootViewController: ViewController1)
                   self.present(ViewNavigationController, animated: true, completion: nil)
               } catch let err {
                   print(err)
               }

}

这是相关的主页代码:

class ViewController: UIViewController, UITextFieldDelegate {



@IBOutlet weak var emailField: UITextField!

@IBOutlet weak var passwordField: UITextField!

var userUID: String!
var databaseRef: DatabaseReference!

override func viewDidLoad() {

    super.viewDidLoad()

    databaseRef = Database.database().reference()


    self.passwordField.delegate = self
    self.emailField.delegate = self

    emailField.attributedPlaceholder = NSAttributedString(string: "Email",
    attributes: [NSAttributedString.Key.foregroundColor: UIColor.gray])

    passwordField.attributedPlaceholder = NSAttributedString(string: "Password",
    attributes: [NSAttributedString.Key.foregroundColor: UIColor.gray])



}
 override func viewDidAppear(_ animated: Bool) {
    if let _ = KeychainWrapper.standard.string(forKey: "uid") {
        self.performSegue(withIdentifier: "tohome", sender: nil)
    }
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
     @IBAction func signInPressed(_ sender: Any) {

   Auth.auth().createUser(withEmail: (emailField.text ?? ""), password: (passwordField.text ?? ""))  { (user, error) in
       if let _eror = error {
           //something bad happning
           print(_eror.localizedDescription )
        let alert = UIAlertController(title: "Error", message: "Invalid Entry or Duplicate.", preferredStyle: UIAlertController.Style.alert)
                             let action = UIAlertAction(title: "Ok", style: .default, handler: nil)
                             alert.addAction(action)
                             self.present(alert, animated: true, completion: nil)

       }else{
           //user registered successfully
           print(user as Any)
                 if let userID = user?.uid {
                                           KeychainWrapper.standard.set((userID), forKey: "uid")

                                           let databaseRef = Database.database().reference()


databaseRef.child("people").child(userID).child("users").setValue(self.emailField.text!)

databaseRef.child("people").child(userID).child("postID").setValue(userID)

                                           self.performSegue(withIdentifier: "tohome", sender: nil)
                                       }

       }
    }
}

 @IBAction func loginInPressed(_ sender: Any) {
 Auth.auth().signIn(withEmail: (emailField.text ?? ""), password: (passwordField.text ?? ""))  { (user, error) in
 if let _eror = error {
               //something bad happning
               print(_eror.localizedDescription )
            let alert = UIAlertController(title: "Error", message: "Incorrect Email or Password.", preferredStyle: UIAlertController.Style.alert)
                                 let action = UIAlertAction(title: "Ok", style: .default, handler: nil)
                                 alert.addAction(action)
                                 self.present(alert, animated: true, completion: nil)

           }else{
               //user registered successfully
               print(user as Any)
                    if let userID = user?.uid {
                        KeychainWrapper.standard.set((userID), forKey: "uid")
                        self.performSegue(withIdentifier: "tohome", sender: nil) }

           }
        }
}

Answer 1

问题隐藏在这一行:

@IBAction func unwindToRed(_ sender: Any) {
    do {
          try Auth.auth().signOut()
          let ViewController1 = ViewController() // <-- This is the problem
          let ViewNavigationController = UINavigationController(rootViewController: ViewController1)
          self.present(ViewNavigationController, animated: true, completion: nil)
     } catch let err {
          print(err)
     }

}

因为您使用 Storyboard来创建 View ，所以您应该从 Storyboard实例化您的 View Controller 。要正确执行此操作，请参阅 Creating View Controllers from Storyboard 。

如果您是 iOS 开发新手或者您不知道为什么需要这样做，请参阅此 post这将解释从 Storyboard实例化 View Controller 与创建新实例。