swift 4 : Firebase still creating user even on error?

Question

我有一个在按下注册按钮时运行的函数，该函数使用 Auth.auth().createUser(withEmail: email,password:password) 来注册用户(如果用户不注册)已经有一个帐户，或者没有错误。然后我将它们添加到数据库中并登录。如果有任何错误，我会显示错误并返回。

但是，即使用户以前从未注册过并且数据库没有其信息，我也会收到 .emailAlreadyInUse 错误，之后用户仍然会添加到数据库中。 Firebase 似乎正在创建帐户，然后给我一个错误。这是为什么？我该如何解决它？

这是我的代码:

@IBAction func registerPressed(_ sender: Any?) {

        //set up new user using Firebase
        if (firstNameTextField.text! == "" && emailTextField.text! == "" && passwordTextField.text! == "") {
            self.topMessage.text = "Please enter your details"
        } else if (firstNameTextField.text! == "" && emailTextField.text! != "" && passwordTextField.text! != "") {
            self.topMessage.text = "Please enter your first name"
        } else {
            Auth.auth().createUser(withEmail: emailTextField.text!, password: passwordTextField.text!) {
                (user, error) in
                if error != nil {
                    print(error!)
                    if let errCode = AuthErrorCode(rawValue: error!._code) {
                        switch errCode {
                        case .weakPassword:
                            self.topMessage.text = "Password too short"
                            break
                        case .emailAlreadyInUse:
                            self.topMessage.text = "Email already in use"
                            break
                        case .invalidEmail:
                            self.topMessage.text = "Invalid email"
                            break
                        case .missingEmail:
                            self.topMessage.text = "Please enter an email"
                            break
                        default:
                            self.topMessage.text = "Error :( Please try again!"
                            break
                        }
                    }
                    return
                }
                else if let user = user {

                    let username = self.firstNameTextField.text!
                    let name = self.firstNameTextField.text!
                    let email = self.emailTextField.text!
                    let profileImage = ""
                    let password = self.passwordTextField.text!

                    let newUser = User(uid: user.uid, username: username, name: name, profileImage: profileImage, email: email, userCoins: 0, questsComplete: 0, rewardsRedeemed: 0, streak: 0, isSubscribed: false)

                    newUser.save(completion: { (error) in
                        if error != nil {
                            print(error!)
                        } else {
                            //successfully initialised
                            Auth.auth().signIn(withEmail: email, password: password, completion: { (user, error) in
                                if let error = error {
                                    print(error)
                                } else {
                                    self.performSegue(withIdentifier: "registerToMainMap", sender: self)
                                }
                            })

                        }
                    })

                }

            }
        }
    }

Answer 1

根据文档Firebase documentation on errors

FIRAuthErrorCodeEmailAlreadyInUse Indicates the email used to attempt sign up already exists. Call fetchProvidersForEmail to check which sign-in mechanisms such user used, and prompt the user to sign in with one of those.

那么，这样的事情会给你带来什么？

Auth.auth().fetchProviders(forEmail: emailTextField.text!) { (email,completion) in
   print("email is ", email!)
   print("completion is ", completion!)
}