A value of type 'GoogleSignInAccount?' can't be assigned to a variable of type 'GoogleSignInAccount'

Question

This is my code:

// ignore: import_of_legacy_library_into_null_safe
import 'package:google_sign_in/google_sign_in.dart';
import 'package:firebase_auth/firebase_auth.dart';

Future<Map<String, dynamic>> signInWithGoogle() async {
  final GoogleSignInAccount googleUser = await GoogleSignIn().signIn();
  final GoogleSignInAuthentication googleAuth = await googleUser.authentication;
  final credential = GoogleAuthProvider.credential(
    accessToken: googleAuth.accessToken,
    idToken: googleAuth.idToken,
  );

  return {
    "email": googleUser.email,
    "photoUrl": googleUser.photoUrl,
    "credentials": await FirebaseAuth.instance.signInWithCredential(credential),
  };
}

Future<bool> signInWithEmail(String email, String password) async {
  try {
    FirebaseAuth.instance.
    signInWithEmailAndPassword(email: email, password: password);
    return true;
  } on FirebaseAuthException catch(e){
    print(e.code);
    return false;
  }
}



Future<bool> signUpWithEmail(String email, String password) async {
  try {
    FirebaseAuth.instance.
    createUserWithEmailAndPassword(email: email, password: password);
    return true;
  } on FirebaseAuthException catch(e){
    print(e.code);
    return false;
  }
}

This is the suggestion that flutter provides, but I don't know what to do:

A value of type 'GoogleSignInAccount?' can't be assigned to a variable of type 'GoogleSignInAccount'. Try changing the type of the variable, or casting the right-hand type to 'GoogleSignInAccount'.

How can I solve this issue?

Thanks for any help you can provide

Answer 1

As the error said, GoogleSignIn().signIn() returns you GoogleSignInAccount? that means it could be null and you can't pass it to variable type GoogleSignInAccount . You need to change googleUser 's type to GoogleSignInAccount? .

final GoogleSignInAccount? googleUser = await GoogleSignIn().signIn();

after that you need to change your return map in signInWithGoogle to this:

final GoogleSignInAuthentication? googleAuth = await googleUser?.authentication;

...
return {
    "email": googleUser?.email ?? '',
    "photoUrl": googleUser?.photoUrl ?? '',
    "credentials": await FirebaseAuth.instance.signInWithCredential(credential),
  };

what I did is that use ? on googleUser , and set the default value ( ' ' ) incase that googleUser was null . you need to repeat this for credential too and provide it default value that good for it incase it get null too.