Prevent duplicate users with Firebase Database, Swift 3

Question

I try to prevent the creation of already existing usernames.

This is my code where I upload usernames to the database:

ref?.child(\"users\").child(FIRAut         


        

Answer 1

You can only query for values that are at a directly under the reference you query at. For your case that would be with a data model like:

Database_App {
    users {
        -3bSRmS4PHXUwsr7XbMBwgPozNfK2: "sebas.varela"
    }     
} 

This will work in your code, but is hard to get secure and performant. The more common approach is to work with a extra node where you map user names to uids:

Database_App {
    userNames {
        "sebas,varela": "-3bSRmS4PHXUwsr7XbMBwgPozNfK2"
    }     
} 

In this case the node essentially allows a user to claim their name. The advantage of this system is that the keys are automatically guaranteed to be unique on the server, no client-side code needed for that part.

You will want to:

• add security rules that ensure a user can only claim a username that hasn't been claimed yet
• also in these security rules allow a user to release their claim on a username
• add client-side code to handle conflicts in a nicer way than the default "permission denied" error you'll get from the server