How do I listen to changes in Firebase custom claims?-CodePudding

I am creating an app in Ionic Vue with Firebase as my backend. I am using Firebase custom claims to assign user roles ('paid user' or 'free user') and I have set up a cloud function that assign the roles without any problems.

Now I want my app to be able to listen to changes in the custom claims, so that if a free user becomes a paid user, the app will know in realtime. Current I only get the updated custom claim if I reload the app by using onAuthStateChanged like this:

onAuthStateChanged(auth, () => {
  if (auth.currentUser) {
    auth.currentUser.getIdTokenResult(true).then((idTokenResult) => {
      console.log(idTokenResult);
      auth.currentUser.subscriber = idTokenResult.claims.subscriber;
    });
  }
// Run app
});

What would be the best approach to listen for changes when the user gets assigned a new role?

CodePudding user response：

I want my app to be able to listen to changes in the custom claims

This is not possible with the Fireabse Authentication service. You should implement your own mechanism: For example, having a Firestore document per user and save the user's role in this document. This way you can set a realtime listener to the user's Firestore document and be alerted in your front end that the user's role has changed.

Note that this will only implement an alerting system. You'll still have to refresh the token with firebase.auth().currentUser.getIdTokenResult() (as shown in the doc) in order to reflect the new role in your front-end.

CodePudding user response：

One way to listen for changes in the custom claims of a Firebase user is to use the onIdTokenChanged method provided by the Firebase Auth library. This method allows you to register a listener that will be called whenever the user's ID token changes, including when the custom claims have been updated.

Here's an example of how you could use the onIdTokenChanged method in your Ionic Vue app:

import firebase from 'firebase/app';

firebase.auth().onIdTokenChanged((user) => {
  if (user) {
    // Get the latest ID token and custom claims
    user.getIdTokenResult(true).then((idTokenResult) => {
      console.log(idTokenResult);
      auth.currentUser.subscriber = idTokenResult.claims.subscriber;
    });
  }
});

This listener will be called whenever the user's ID token changes, including when the custom claims are updated. You can then update the app state or perform any other necessary actions based on the updated custom claims.

Keep in mind that the onIdTokenChanged method will only be triggered when the user's ID token changes, which may not happen every time the custom claims are updated. However, this should be sufficient for most use cases, as the ID token is typically refreshed on a regular basis.