User management with Firebase in SwiftUI where to start?

Question

I'm trying to understand back end development with Firebase in SwiftUI, I have developed a small application in which we can actually login with Firebase Auth. I would like to display a pop-up when the user logs in for the first time, Firebase doesn't have a function already done for that so I would like to code one but where to start?

I wanted to get the UID of the user when he logs in and put it in the "user_data" database if it wasn't already there otherwise ignore the rest of my function. If it is not there then display a pop-up in which he can choose a flag that will be assigned to him (for example a city) and then display the restaurants in his city for example.

The question may seem silly but I am new to this field and I would like to improve because it interests me a lot and seeks to understand and document me as much as possible on the back end of swiftUI.

Thank you for your precious help and advice.

Answer 1

           Auth.auth().signIn(with: credential) { (result, error) in
                if error == nil{
                    if result?.additionalUserInfo!.isNewUser == true{
                       //is a new user
                    }
                }
            }