How do I update a FirebaseUser's phone number in firebase_auth? - firebase

Question

In my Flutter app I use Firebase's phone number authentication as my main form of authentication. After authenticating, I create a user in my users collection with these details:
{
phoneNumber: FirebaseAuth.instance.currentUser().phoneNumber,
displayName: 'Comes from user textbox',
...
}
But say one day a user want's to change their phone number. How do I do this? Because I cannot simply change the user's phone number in the document, because the phone number needs to be authenticated. And after authentication, the user gets a new authUID. Which should then be a new user?
Could someone explain the logic behind a user that wants to keep their profile details but change their number.

Answer 1

In order to achieve this, you can use User.updatePhoneNumber. This allows you to update the phone number of a user.
You would use it in the same manner that you also authenticated with phone number in the first place (using signInWithCredential), i.e. you retrieve a credential using FirebaseAuth.verifyPhoneNumber and pass the credential that you get from either verificationCompleted or your user when they enter the SMS code they received. I will only sketch out what this would look like as I assume that you know how to perform this task:
FirebaseAuth.instance.verifyPhoneNumber(
phoneNumber: phoneNumber,
timeout: const Duration(minutes: 2),
verificationCompleted: (credential) async {
await (await FirebaseAuth.instance.currentUser()).updatePhoneNumber(credential);
// either this occurs or the user needs to manually enter the SMS code
},
verificationFailed: null,
codeSent: (verificationId, [forceResendingToken]) async {
String smsCode;
// get the SMS code from the user somehow (probably using a text field)
final AuthCredential credential =
PhoneAuthProvider.getCredential(verificationId: verificationId, smsCode: smsCode);
await (await FirebaseAuth.instance.currentUser()).updatePhoneNumber(credential);
},
codeAutoRetrievalTimeout: null);
When updatePhoneNumber is called, you probably also want to update your database document. Alternatively, you could listen to onAuthStateChanged and update your document this way.

Answer 2

async function save(phone: string, e) {
e.preventDefault();
const { currentUser:fuser } = firebase.auth();
if(fuser && fuser.phoneNumber !== phone) {
try {
const verifier = new firebase.auth.RecaptchaVerifier('recaptcha-container', {
callback: (response) => console.log('callback', response),
size: 'invisible',
});
const phoneProvider = new firebase.auth.PhoneAuthProvider();
const id = await phoneProvider.verifyPhoneNumber(phone, verifier);
const code = window.prompt('Bitte zugeschickten Code eingeben');
const cred = firebase.auth.PhoneAuthProvider.credential(id, code);
await fuser.updatePhoneNumber(cred);
console.log('phone number changed', id, cred, fuser);
setSuccess(true);
} catch(e) {
console.error(e);
}
}
}