Firebase: setting additional user properties

Question

I'd like to add a property to a Firebase user object. The user documentation says that I can only store additional properties using the Firebase real time database.

I am unsure on how this can works in practice.

What does the following mean in practice?

You cannot add other properties to the Firebase User object directly; instead, you can store the additional properties in your Firebase Realtime Database.

I interpret it as following:

"you cannot modify properties of a FIRUser object but you can combine this with additional objects"

I found the set function documentation which I interpet in this way:

  var userRef = ref.child("users");   userRef.set({     newfield: "value"   }); 

Is this a sensible approach?

Answer 1

You're almost there. In the legacy Firebase documentation, we had a section on storing such additional user data.

The key is to store the additional information under the user's uid:

    let newUser = [         "provider": authData.provider,         "displayName": authData.providerData["displayName"] as? NSString as? String     ]     // Create a child path with a key set to the uid underneath the "users" node     // This creates a URL path like the following:     //  - https://<YOUR-FIREBASE-APP>.firebaseio.com/users/<uid>     ref.childByAppendingPath("users")        .childByAppendingPath(authData.uid).setValue(newUser) 

I've added a note that we should add this information in the new documentation too. We just need to find a good spot for it.

Answer 2

According to the Custom Claims documentation,

The Firebase Admin SDK supports defining custom attributes on user accounts. [...] User roles can be defined for the following common cases:

• Add an additional identifier on a user. For example, a Firebase user could map to a different UID in another system.

[...] Custom claims payload must not exceed 1000 bytes.

However, do this only for authentication-related user data, not for general profile information, per the Best Practices:

Custom claims are only used to provide access control. They are not designed to store additional data (such as profile and other custom data). While this may seem like a convenient mechanism to do so, it is strongly discouraged as these claims are stored in the ID token and could cause performance issues because all authenticated requests always contain a Firebase ID token corresponding to the signed in user.

Use custom claims to store data for controlling user access only. All other data should be stored separately via the real-time database or other server side storage.