Using FirebaseAuth verifyPhoneNumber in flutter? - flutter

Question

Hey I am trying to use Firebase Auth verifyPhoneNumber in Flutter.
I am constantly getting my msg in onTap function as null. I tried declaring a variable in registerToFb function but I am not able to update its value. How do I solve it?
Following is the function from where I am calling the firebaseAuth.verifyPhoneNymber() method.
onTap: () async {
setState(() => isLoading = true);
String msg = await _auth.registerToFb(
"+91$truephoneNumber", context);
print(msg);
},
Following is where I am defining my function.
class AuthenticationService {
final FirebaseAuth _firebaseAuth;
AuthenticationService(this._firebaseAuth);
Future registerToFb(String phoneNumber, BuildContext context) async {
String result = " ";
await _firebaseAuth.verifyPhoneNumber(
phoneNumber: phoneNumber,
timeout: const Duration(seconds: 30),
verificationCompleted: (PhoneAuthCredential credential) async {
UserCredential authresult =
await _firebaseAuth.signInWithCredential(credential);
User user = authresult.user;
_getUserFromFirebase(user);
result = "signedUp";
},
verificationFailed: (FirebaseAuthException e) {
String error = e.code == 'invalid-phone-number'
? "Invalid number. Enter again."
: "Can Not Login Now. Please try again.";
result = error;
},
codeSent: (String verificationId, int resendToken) {
result = "verified";
},
codeAutoRetrievalTimeout: (String verificationId) {},
);
}
return result;
}
Help me, please. Thanks

Answer 1

The problem is that you aren't returning anything in your function. And even when you try to save a value from inside the callbacks, the future from verifyPhoneNumber resolves before those callbacks get called.
You need to be awaiting the right thing. You shouldn't await the future returned from verifyPhoneNumber. You should await a new future that doesn't resolve until you get a result from one of the callbacks. This means you need to create your own Future which you can manually resolve specifically when you need it to. You can do this with a Completer:
Future<String> registerToFb(String phoneNumber, BuildContext context) {
final completer = Completer<String>();
_firebaseAuth.verifyPhoneNumber(
phoneNumber: phoneNumber,
timeout: const Duration(seconds: 30),
verificationCompleted: (PhoneAuthCredential credential) async {
UserCredential authresult =
await _firebaseAuth.signInWithCredential(credential);
User user = authresult.user;
_getUserFromFirebase(user);
completer.complete("signedUp");
},
verificationFailed: (FirebaseAuthException e) {
String error = e.code == 'invalid-phone-number'
? "Invalid number. Enter again."
: "Can Not Login Now. Please try again.";
completer.complete(error);
},
codeSent: (String verificationId, int resendToken) {
completer.complete("verified");
},
codeAutoRetrievalTimeout: (String verificationId) {
completer.complete("timeout");
},
);
return completer.future;
}