将StateNotifier改为Notifier后，如何重写NotifierProvider并调用其他Provider

问题 #

已将StateNotifier类修改为Notifier类，但不清楚如何重写对应的Provider。原StateNotifier类会将其他Provider监听的值作为实例变量使用，请问如何在NotifierProvider中调用其他Provider所监听的值？

给出的新Notifier类代码：

class CommunityController extends Notifier<bool> {
  final CommunityRepository _communityRepository;
  final StorageRepository _storageRepository;
  final Ref _ref;
  CommunityController({
    required CommunityRepository communityRepository,
    required StorageRepository storageRepository,
    required Ref ref,
  })  : _communityRepository = communityRepository,
        _storageRepository = storageRepository,
        _ref = ref;

  @override
  bool build() {
    return false;
  }

  void createCommunity(String name, BuildContext context) async {
    state = true;
    final uid = _ref.read(userProvider)?.uid ?? '';
    Community community = Community(
      id: name,
      name: name,
      banner: Constants.bannerDefault,
      avatar: Constants.avatarDefault,
      members: [uid],
      mods: [uid],
    );

    final res = await _communityRepository.createCommunity(community);
    state = false;
    res.fold((l) => showSnackBar(context, l.message), (r) {
      showSnackBar(context, 'Community created successfully!');
      Routemaster.of(context).pop();
    });
  }

  Stream<Community> getCommunityByName(String name) {
    return _communityRepository.getCommunityByName(name);
  }
}

待改写的原StateNotifierProvider代码：

final communityControllerProvider = StateNotifierProvider<CommunityController, bool>((ref) {
  final communityRepository = ref.watch(communityRepositoryProvider);
  final storageRepository = ref.watch(storageRepositoryProvider);
  return CommunityController(
    communityRepository: communityRepository,
    storageRepository: storageRepository,
    ref: ref,
  );
});

解决方案 #

1. 优化Notifier类的写法 #

Riverpod的新Notifier体系内置了ref属性，无需手动在构造函数中传入Ref。同时可以将依赖的仓库通过ref.watch在build方法中获取，自动监听仓库Provider的变化：

class CommunityController extends Notifier<bool> {
  late final CommunityRepository _communityRepository;
  late final StorageRepository _storageRepository;

  @override
  bool build() {
    // 在build方法中监听仓库Provider，变化时自动重建Notifier
    _communityRepository = ref.watch(communityRepositoryProvider);
    _storageRepository = ref.watch(storageRepositoryProvider);
    return false;
  }

  void createCommunity(String name, BuildContext context) async {
    state = true;
    // 直接使用内置ref读取其他Provider的值
    final uid = ref.read(userProvider)?.uid ?? '';
    Community community = Community(
      id: name,
      name: name,
      banner: Constants.bannerDefault,
      avatar: Constants.avatarDefault,
      members: [uid],
      mods: [uid],
    );

    final res = await _communityRepository.createCommunity(community);
    state = false;
    res.fold((l) => showSnackBar(context, l.message), (r) {
      showSnackBar(context, 'Community created successfully!');
      Routemaster.of(context).pop();
    });
  }

  Stream<Community> getCommunityByName(String name) {
    return _communityRepository.getCommunityByName(name);
  }
}

2. 改写为NotifierProvider #

替换原StateNotifierProvider为NotifierProvider，无需手动传入参数，直接关联CommunityController即可：

final communityControllerProvider = NotifierProvider<CommunityController, bool>(
  CommunityController.new,
);

关键说明 #

• 调用其他Provider：在Notifier的方法中，直接用ref.read()（单次读取，不监听变化）或ref.watch()（持续监听，值变化时触发重建）获取目标Provider的值即可。
• 依赖管理：在build方法中通过ref.watch获取仓库，能确保仓库实例更新时，Notifier自动重建并使用最新实例，符合Riverpod的响应式设计。

内容的提问来源于stack exchange，提问作者wasa-bi