firebase - "The operator '[]' isn't defined" error when using .data[] in flutter firestore

Question

I am learning to use firestore in flutter following Net Ninja's tutorial on youtube. After user authenticatin was done this guy added user records to the database whenever a new user is created, for doing this a new model was added passing 1 String named "name" and from what I undertstood for calling that he mapped the model and then used .data['name'] to get that string from the model(string was called name) and when doing this, I got the error The operator '[]' isn't defined for the type 'Map<String, dynamic> Function()' Why am I getting this error?

username model

class Username {
  final String name;
  Username({ this.name });
}

databse.dart file (the following code is wrapped in a class called DatabaseService)

  List<Username> _usernameListFromSnapshot(QuerySnapshot snapshot) {
    return snapshot.docs.map((doc){
      return Username(
        name: doc.data['name'] ?? '',
      );
    }).toList();
  }

auth.dart

  Future registerWithEmailAndPassword(String email, String password) async {
    try {
      UserCredential result = await _auth.createUserWithEmailAndPassword(email: email, password: password);
      User user = result.user;

      // create a new document for the user with uid
      await DatabaseService(uid: user.uid).updateUserData('user123');
      return _userFromFirebaseUser(user);
    } catch(e) {
      print(e.toString());
      return null;
    }
  }

if you have any questions or need to see more code, please let me know in the comments

Answer 1

Waitting for answers