CODEWITHSUNDEEP
flutterfirebasedartflutter-providerstate-management
Robinson T
Robinson T

Reputation: 101

Null Check Operator used on a null value due to provider class

I'm getting the 'null check operator used on a null value' when I try to access specific screens.

I blocked out my 'user_provider' custom class as well as parts of the code where it's used and it displays normally (no red screen) but without those screens.

This is the custom class

import 'package:flutter/widgets.dart';
import 'package:purple/models/user.dart';
import 'package:purple/resources/auth_methods.dart';

class UserProvider with ChangeNotifier {
  User? _user;
  final AuthMethods _authMethods = AuthMethods();

  User get getUser => _user!;

  Future<void> refreshUser() async {
    User user = await _authMethods.getUserDetails();
    _user = user;
    notifyListeners();
  }
}

I underdertand this could be as a result of the bang operator in line 9 but I'm new to fluttr and have no idea how to go about it.

Upvotes: 5

Views: 806

Answers (2)

HasanAlyazidi
HasanAlyazidi

Reputation: 619

You should not call getUser if it returns null. Maybe you did not load the user from _authMethods.getUserDetails().

So here is an idea, check if user is logged in first then call getUser

import 'package:flutter/widgets.dart';
import 'package:purple/models/user.dart';
import 'package:purple/resources/auth_methods.dart';

class UserProvider with ChangeNotifier {
  User? _user;
  final AuthMethods _authMethods = AuthMethods();

  User get getUser => _user!;

  bool get isLoggedIn => _user != null; // <---------- added

  Future<void> refreshUser() async {
    User user = await _authMethods.getUserDetails();
    _user = user;
    notifyListeners();
  }
}

then in a screen or a widget:

if (userProvider.isLoggedIn) {
   // TODO: do what you want such as returning user's name
   return userProvider.getUser.name;
}

Upvotes: 1

My Car
My Car

Reputation: 4556

Try this:

import 'package:flutter/widgets.dart';
import 'package:purple/models/user.dart';
import 'package:purple/resources/auth_methods.dart';

class UserProvider with ChangeNotifier {
  User _user;
  final AuthMethods _authMethods = AuthMethods();

  User get getUser => _user;

  Future<void> refreshUser() async {
    User user = await _authMethods.getUserDetails();
    _user = user;
    notifyListeners();
  }
}

Upvotes: 0

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