Firebase listen to when auth "loading" has completed

Question

I am trying to achieve the following flow:
1. Wait for app to load
2. Check if user exists
2.1 If doesn't, sign-up as anonymous
2.1.1 Create new collection using user ID
2.2 If does, pull existing collection using user ID

Reading through the specs I found the following way to persist users Auth State:

firebaseInstance.auth().setPersistence(firebaseAuth.Auth.Persistence.LOCAL)
      .then(function() {
        // Existing and future Auth states are now persisted in the current
        // session only. Closing the window would clear any existing state even
        // if a user forgets to sign out.
        // ...
        // New sign-in will be persisted with session persistence.
        return firebaseInstance.auth().signInAnonymously().catch(function(error) {
          // Handle Errors here.
          var errorCode = error.code;
          var errorMessage = error.message;
          // ...
        })
      })
      .catch(function(error) {
        // Handle Errors here.
        var errorCode = error.code;
        var errorMessage = error.message;
      })

And later listen for the state change with:

firebaseInstance.auth().onAuthStateChanged(user => {
        if (user) {
          // User is signed in.
          var isAnonymous = user.isAnonymous
          var uid = user.uid

          const test = firebaseInstance.auth().currentUser
          // ...
          debugger
        } else {
          // User is signed out.
          // ...
        }
        // ...
      })

My understanding I can imagine that when firebase finishes initialising it pulls user from IndexedDB, sign-in completes and the user's data becomes available. (please correct me if I am wrong)

The issue Executing firebaseInstance.auth().currentUser before the firebase finishes completing it's internal logic returns null, this makes me wonder if it's possible to listen for event when firebase auth completes it's internal tasks --> check for the current user, and if even after that there is still no user --> signIn with a new anonymus one.

Confusion point P.S: I am also confused why triggering signInAnonymously() time after time still returns the same user ID. It makes me doubt if I actually picked up the "right" way to achieve the functionality. If somebody can came up with a better implementation of the functionality flow I will appreciate it a lot :)

For people also looking into this issue a part from accepted answer you can read the comment sections of the accepted answer in this question --> https://stackoverflow.com/questions/49492187/test-if-there-is-a-pending-firebase-authentication — volna, Aug 07 '19 at 06:43

Christopher Peisert · Accepted Answer · 2019-08-07T02:58:29.413

The Firebase documentation for setPersistence(persistence) states:

The default for web browser apps and React Native apps is 'local' (provided the browser supports this mechanism) whereas it is 'none' for Node.js backend apps.

Therefore, there is no need to explicitly call setPersistence(firebaseAuth.Auth.Persistence.LOCAL).

1. Wait for the app to load

You could use vanilla Javascript, such as:

window.onload = function() {
  // Handle Firebase auth.
}

2. Check if user exists, and if not, sign-in anonymously

var user = firebase.auth().currentUser;

if (user) {
  // User is signed in.
  var isAnonymous = user.isAnonymous
  var uid = user.uid
} else {
  // No user is signed in.
  firebaseInstance.auth().signInAnonymously().catch(function(error) {
      // Handle Errors here.
      var errorCode = error.code;
      var errorMessage = error.message;
      // ...
  })
}


// Get user once anonymously signed in.
firebaseInstance.auth().onAuthStateChanged(user => {
  if (user) {
    // User is signed in.
    var isAnonymous = user.isAnonymous
    var uid = user.uid
  } else {
    // User is signed out (does not 'exist')
    firebaseInstance.auth().signInAnonymously().catch(function(error) {
      // Handle Errors here.
      var errorCode = error.code;
      var errorMessage = error.message;
      // ...
    })
  }
}

Thank you for the explanation, I've indeed misunderstood that onAuthStateChanged triggers no matter if credentials where actually stored or not and will just returns null in case user is signed out. — volna, Aug 07 '19 at 06:41

Firebase listen to when auth "loading" has completed

1 Answers1

1. Wait for the app to load

2. Check if user exists, and if not, sign-in anonymously