How do I update Flutter's Riverpod values from business logic?-CodePudding

When using Flutter and Riverpod, how do I update its values from my business logic?

I understand that I can get and set values from the UI side.

class XxxNotifier extends StateNotifier<String> {
  XxxNotifier() : super("");
}

final xxxProvider = StateNotifierProvider<XxxNotifier, int>((ref) {
  return XxxNotifier();
});

class MyApp extends HookConsumerWidget {
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    // getValue
    final String value = ref.watch(xxxProvider);

    // setValue
    context.read(xxxProvider).state = "val";

    return Container();
  }
}

This method requires a context or ref.

How do I get or set these states from the business logic side?

Passing a context or ref from the UI side to the business logic side might do that, but I saw no point in separating the UI and business logic. Perhaps another method exists.

Perhaps I am mistaken about something. You can point it out to me.

CodePudding user response：

You can pass ref in your XxxNotifier class:

class XxxNotifier extends StateNotifier<String> {
  XxxNotifier(this._ref) : super("");

  final Ref _ref;

  void setNewState() {
    state = 'to setting';
    // use `_ref.read` to read state other provider
  }
}

final xxxProvider = StateNotifierProvider<XxxNotifier, int>((ref) {
  return XxxNotifier(ref);
});

// or using tear-off
final xxxProvider = StateNotifierProvider<XxxNotifier, int>(XxxNotifier.new);

CodePudding user response：

You can create methods in your XxxNotifier class to modify the state of your provider.

For example, your notifier class can look like this.

class TodosNotifier extends StateNotifier <List<Todo>> {
  TodosNotifier(): super([]);

  void addTodo(Todo todo) {
    state = [...state, todo];
  }

}

You can then read the provider in a callback.

ref.read(xxxProvider.notifier).addTodo(todo);