如何在用户创建期间使用 Firebase Auth 验证字段服务器端？

Question

I'm trying to use Firebase Auth to create a new user, but I want to validate some fields (pattern matching) using Firestore Security Rules before creating a new account. How can I do that?

In the completion handler for the createUser(withEmail: , password:) function, I am performing some writes to Firestore on successful account creation.

I am facing a problem where sometimes the writes to Firestore may not be successful due to Firestore Secuity Rules (Pattern matching). In this case the write fails but the new user account is still created (since writes are being attempted in completion handler).

// Create User Method - Firebase Auth & Swift

Auth.auth().createUser(withEmail: self.emailTextField.text!, password: self.passwordTextField.text!) { (result, error) in
                    if error != nil {
                        print(error?.localizedDescription)
                    } else { 
                        let userName = [
                            userName:self.userNameTextField.text!
                        ]

// Writing field Data to Firestore

Firestore.firestore().collection("users").document(self.userNameTextField.text!).setData(userName) {(err) in
                            if err != nil {

// Rather than throwing a fatalError, how can I ensure new account creation is cancelled so that feedback can be given on the issue with entered field data?                              

fatalError()
                            }

I want to ensure a user account is not created in case writes to Firestore are unsuccessful due to a conflict with Firestore Security Rules.

Answer 1

Firebase Authentication doesn't have any security rules. There's currently no way to check if incoming account properties are valid before a user gets created. Security rules only apply to data read and written directly to Cloud Firestore (or Realtime Database, or Cloud Storage) from a mobile or web client.

The only thing you could do is use a Cloud Functions auth trigger to check the account properties after it was created, then delete or deactivate the account if something is wrong.