Question 221551 in Flutter Question posted in
The official Flutter documentation can be found here.

Flutter Riverpod does not catch List<Map>'s nested value changes

final filterProvider = StateProvider<List<Map>>((ref) => [
      {'text': 'rating', 'onOrOff': true},
      {'text': 'km', 'onOrOff': true},
    ]);

I have this filterProvider. And I am trying to update the value of ‘onOrOff’.

ref.watch(filterProvider.notifier).state[i]['onOrOff'] = onOffVal;

When I do this way, Riverpod does not change the value immediately, how can I adjust the value and make Riverpod to apply changes right away?

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2

Answers


  1. 0

    In riverpod the state provided with a StateProvider is supposed to be immutable. You cannot modify it, you need to re-assign it.

    You can read

    It is typically used for:

    • exposing an immutable state which can change over time after reacting to custom events.
    • centralizing the logic for modifying some state (aka "business logic") in a single place, improving maintainability over time.

    in riverpod’s documentation

    final filter = [...ref.read(filterProvider)]; // Copies the list.
filter[i]['onOrOff'] = onOffVal;
ref.read(filterProvider.notifier).state = filter;
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  2. 0

    This is part of why StateNotifier and StateProvider should not be used in modern Riverpod applications. Instead, you should be constructing a Notifier-based provider, and provide mutation methods to update your state. The Notifier can use combinations of assigning to state (as the previous StateNotifier did) and/or calling ref.notifyListeners() (as the previous ChangeNotifier did).

    But please, stop using StateNotifier, ChangeNotifier, and StateProvider with Riverpod! They are all effectively deprecated.

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