Global value is not initalized

Question

I have a global variable User? current_atlas_user that is in file 'Constants.dart'. I want to initialize it from the main.dart file. To do it I am trying this:

Future<void> setAtlasUser(String email) async {
  final app = App(AppConfiguration(APP_ID));
  current_atlas_user =
      await app.logIn(Credentials.emailPassword(email, ATLAS_PASSWD));
}

This function is called in the end of the @override void initState() function. And after using the debugger I made sure that the code is reaching the Future<void> setAtlasUser(String email) function.

My problem is here

  @override
  Widget build(BuildContext context) {
    List<Widget> _screens = [NotDoneScreen(), const DoneScreen()];

The NotDoneScreen() assumes that current_atlas_user is already defined. But when running the code it fails saying that it is still null.

I know that initState() should run before build() and therefore I am confused about this problem.

Answer 1

You can use FutureBuilder to wait for current_atlas_user to initialize. While waiting for future to finish, you can show some sort of loading indicator. Here is how I would structure it:

1. create a local variable to store the future:

Future<void>? _current_atlas_user_future;

2. assign value to local variable in initState

@override
  void initState() {
    super.initState();
    _current_atlas_user_future = setAtlasUser(email);
  }

3. now add FutureBuilder to build method

@override
  Widget build(BuildContext context) {
    return FutureBuilder<void>(
       future: _current_atlas_user_future,
        builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.done) {
                 // current_atlas_user should be ready here
                 // load the screens
                 List<Widget> _screens = [NotDoneScreen(), const DoneScreen()];

            } else {
                 // current_atlas_user should be null here

                // show some sort of loading indicator
                return CircularProgressIndicator();
            }
        }
    );
}

Note that _current_atlas_user_future is separate from current_atlas_user . _current_atlas_user_future is just holding reference to a future and current_atlas_user is the value you need in your next screen.