Swift Firebase Authentication - two questions about error handling (I'm not sure how to name these errors)

Question

It's really hard to find a proper title for this question. Please be easy on me. The first part is a check to see if an account exists:

Auth.auth().fetchSignInMethods(forEmail: userEmail, completion: {
            (providers, error) in

            if error != nil {
                self.displayAlertMessage(alertTitle: "Unhandled error", alertMessage: "Undefined error #SignUpViewController_0001");
                return;
            } else if providers != nil {
                self.displayAlertMessage(alertTitle: "Error", alertMessage: "This account is not exist.");
                return;
            }
        })

As you can see, I have something named Unhandled error with message Undefined error. I don't know how to name it properly. Can somebody explain that part to me?

The second one is about getting a localized string - any ideas to make it fancy?

Auth.auth().createUser(withEmail: userEmail, password: userPassword) { user, error in if error == nil && user != nil {
            self.displayAlertMessage(alertTitle: "Success", alertMessage: "Your account created successfully. We send you a verification email.", dismiss: true);
            } else {
            self.displayAlertMessage(alertTitle: "Firebase error", alertMessage: "(error!.localizedDescription)");
            }
        }

Thanks for tips :)

Answer 1

You can handle the Errors this way:

 Auth.auth().fetchSignInMethods(forEmail: email, completion: { (response, error) in

        if let error = error, let errCode = AuthErrorCode(rawValue: error._code)
        {
            switch errCode {
            case .emailAlreadyInUse:
                GeneralHelper.sharedInstance.displayAlertMessage(titleStr: LocalizeConstant.CommonTitles.Alert.rawValue.localizedStr(), messageStr: LocalizeConstant.CommonTitles.Continue.rawValue.localizedStr())
            case .accountExistsWithDifferentCredential:
                GeneralHelper.sharedInstance.displayAlertMessage(titleStr: LocalizeConstant.CommonTitles.Alert.rawValue.localizedStr(), messageStr: LocalizeConstant.CommonTitles.Continue.rawValue.localizedStr())
            default:
                break
            }

            return
        }
}

Here I am getting the errCode using AuthErrorCode provided by Firebase itself and then, I am passing in the received error code using error._code . So, now I can get the type of AuthErrorCode . Using this I am making cases like .emailAlreadyInUser , .accountExistsWithDifferentCredential etc. You can just type . and it will show you all the AuthErrorCodes . So, you can simply handle the error codes in this way.

Now, coming to the second part of the question, ie getting localized string . You can add localization to Firebase , for that you have to select the language code. Auth.auth().languageCode = "en" //For English . But, I do not think that it gives localized errors as there are many more languages than what Firebase supports. This mainly for sending localized emails.

To handle the localization , you have to create your own method as I did. You can see that I have called a function displayAlertMessage in which I am passing the titleStr: LocalizeConstant.CommonTitles.Alert.rawValue.localizedStr() , which is a part of localization.

struct LocalizeConstant {

   enum CommonTitles: String
   {
    case Alert = "common_alert"
   }

}

This value designates to the key given by me in the localization file. If you do not know about localization, you have to do a Google search on it. Let's say I have two Localizable.strings one is in English and the other one is in French . In Localizable.strings(English) , I've written Alert like this:

"common_alert" = "Alert";

And, In French:

"common_alert" = "Alerte!";

So, this is how I have manually added localization in my app. But, to achieve this you have to do two things. 1) You have to set up your appLanguage . 2) You have to call a method which will fetch the values from these keys defined in the Localizable.strings file.

To do this, I have created a method localizedStr() . It is an extension to String and you can use it as follows.

extension String{
  func localizedStr() -> String
  {
    var finalRes = ""

    if let path = Bundle.main.path(forResource: Constants.appLang, ofType: "lproj") //Constants.appLang is "en" here for "English", but you can set accordingly.
    {
        if let bundle = Bundle(path: path)
        {
            finalRes = NSLocalizedString(self, tableName: nil, bundle: bundle, value: " ", comment: " ")
        }
    }

    return finalRes
 }
}

Now, this method localizedStr() will give you a localized string according to your app language. Even, if Firebase provides localized error codes(which I think it does not), it is impossible to get the error description in each language. So this is the best way I came up with. It may not be the best method out there in the world, but it does the task.

PS: To optimize this throughout the app, either you can create an extension to AuthErrorCode or you can create a Helper function where you will just pass the error._code and it will return the localized string . I've added the long way so that you can understand everything in the best way.