Question 76856 in Flutter Question posted in
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Null check operator used on a null value – Riverpod Provider – Flutter

Okay I have a FlutterFire app and using Riverpod to manage the state of my app. I have a Listenable Provider named userProvider where I get the user data from Cloud Fierestore. Note that I have a Stream Provider which updates the userProvider. Here’s what I mean:

Stream<UserModel> getUserData(String uuid) {
    return _users.doc(uuid).snapshots().map(
        (event) => UserModel.fromMap(event.data() as Map<String, dynamic>));
  }

That above is my Stream Provider and here’s what I mean when saying it updates the state of my userProvider:

 void getData(WidgetRef ref, User data) async {
    userModel = await ref
        .watch(authControllerProvider.notifier)
        .getUserData(data.uid)
        .first;
    ref.read(userProvider.notifier).update((state) => userModel);
  }

the above function is in my main.dart file.

My userProvider is like this:

 final userProvider = StateProvider<UserModel?>((ref) => null);

okay so I made it nullable because before sign in there’ll be no user signed in meaning no data to hold.

When I try to use the userProvider I’m getting an error saying null check operator used on a null value but I use a null check operator because I’m certain the user is signed in now and there should be data store to that Provider.

Plaese help me know what is wrong with my code.

Thank you

Tags:

2

Answers


  1. 0

    You need to check first for null before accessing the data in the Provider.

    to check null heres the code:

    final user = userProvider.state;
if (user != null) {
  // use user
} else {
  // handle the case where user is null
}
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  2. 0

    Probably the provider state is reset, although I don’t see you have an .autoDispose modifier. The use this way, you can track at what point in time the state of the provider turns into null:

    final userProvider = StateProvider<UserModel?>((ref) {
  ref.listenSelf((previous, next) {
    print('$next => $previous');
  });

  ref.onDispose(() {
    print('userProvider has been disposed');
  });
});

    I think it’s a great way to stop provider nulling 🙂 Debugging is everything.

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