Implementing a StateNotifier-like class with rearch

[alfalcon90]

For some of the more complex parts of my projects I often use state_notifier and freezed data classes for grouping methods and state under their own respective classes. For example:

class City {
  City({required this.name, required this.population});
  final String name;
  final int population;
}

@freezed
class CityState with _$CityState {
  const factory CityState({
    required List<City> cities,
  }) = _SafetyState;

  factory CityState.initial() => const CityState(
        reports: List.empty(),
      );
}

class CityNotifier extends StateNotifier<CityState> {
  CityNotifier() : super(const CityState.initial());

  void addCity(City newCity) {
    state = state.copyWith(cities: [...state, newCity]);
  }
}

I tried looking through the documentation but couldn't find an example of using rearch for building something like this. The class below is my quick and dirty initial stab at accomplishing a similar thing but I could be way off. Either some official recommended way of doing this in the documentation or a RearchNotifier class that implements it the right way would be great.

class RearchNotifier<State> {
  final _container = CapsuleContainer();

  State build() => throw UnimplementedError();

  (State, void Function(State)) _state(CapsuleHandle use) => use.state(build());

  State get state => _container.read((CapsuleHandle use) => _state(use).$1);

  set state(State value) => _container.read((CapsuleHandle use) {
        final state = _state(use);
        state.$2(value);
      });

  Capsule<R> map<R>(R Function(State s) mapper) =>
      _state.map(((State, void Function(State)) s) => mapper(s.$1));

  void reset() => _container.read((CapsuleHandle use) {
        final state = _state(use);
        state.$2(build());
      });
}

// Which then is used like this
class CityNotifier extends RearchNotifier<CityState> {
  @override
  CityState build() => CityState.initial();

  void addCity(City newCity) {
    state = state.copyWith(cities: [...state, newCity]);
  }
}

[GregoryConrad]

Hi again, finally got to my laptop.

Freezed plays wonderfully with ReArch, but definitely do not use notifiers in conjunction with ReArch. The equivalent is just a capsule with a different API exposed like:

(List<City>, {void Function(City) addCity,}) citiesManager(CapsuleHandle use) {
  final (cities, setCities) = use.state(<City>[]);
  return (
    cities,
    addCity: (city) => setCities([...cities, city]),
    // any other functions you would normally put in your notifier...
  );
}

You can add any other functions to the return value of the capsule as you see fit.

I also would suggest using fast_immutable_collections in the case of immutable lists here. It is much faster and much more ergonomic when handling scenarios like this.

Let me know if you have any other questions!