Question 197373 in Flutter Question posted in
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Flutter – Access Provider in Class

I have a class called NavigatorRepository that I am trying to access, userProvider. How should I be accessing the userProvider inside the NavigatorRepository? I feel like i’ve tried everything, except the right thing…

Here is a snippet from NavigatorRepository

final user = Provider((ref) {
  return ref.watch(userProvider.notifier).getUser();
});
...

class NavigatorRepository {

...

  Future<dynamic> _get(
    String path, {
    Map<String, Object?>? queryParameters,
  }) async {
  
    var x = user; <== How do I get this to work?
}
 

}

UserProvider

class UserNotifier extends StateNotifier<User> {
  UserNotifier()
      : super(User(accessToken: '');

  void setUser(User user) {
    state = user;
  }

  User getUser() {
    return state;
  }
}


final userProvider = StateNotifierProvider<UserNotifier, User>((ref) {
  return UserNotifier();
});
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    Found this thread which covers what I am trying to do.

    https://github.com/rrousselGit/riverpod/issues/295#issuecomment-770384596


  2. 0

    There are many ways to do this.

    1. There is now a newer provider for this purpose, (Async)NotifierProvider:
    final navigatorProvider = NotifierProvider<NavigatorRepository, void>(() {
  return NavigatorRepository();
});

class NavigatorRepository extends Notifier<void> {
  
  @override
  void build() {
    // you can use ref.watch in this method
    User user = ref.watch(userProvider);
  }

  func() {
    // ref is available in any methods of the NavigatorRepository class
    ref.read(...);
  }
    1. The next method is to pass the ref parameter to the class constructor:
    final navigatorProvider = Provider<NavigatorRepository>(NavigatorRepository.new);


class NavigatorRepository {
  NavigatorRepository(this._ref);

  final Ref _ref;

  func() {
    // ref is available in any methods of the NavigatorRepository class
    _ref.read(...);
  }
}
    1. The following way better expresses the principle of implementing dependencies, but follows against the design patterns in Riverpod:
    final navigatorProvider = Provider<NavigatorRepository>((ref) {
  return NavigatorRepository(
    authService: ref.watch(AuthService),
    settingService: ref.watch(SettingService),
    userService: ref.watch(UserService),
  );
});

class NavigatorRepository {
  UserService({
    required AuthService authService,
    required SettingService settingService,
    required UserService userService,
  })  : _authService = authService,
        _settingService = settingService,
        _UserService = userService;

  final AuthService _authService;
  final SettingService _settingService;
  final UserService _userService;

  func() {
    // simply call the method
    User user = _userService.getUser();
  }
}

    The idea is that you pass all necessary dependencies immediately to the constructor of your class. In the end, you know for sure that your class-service only depends on the services that are in the constructor.

    Note also that I have made all services private to avoid outside access. If you don’t need it, make the fields open.

    1. You can simply pass the ref parameter when calling any method:
    class NavigatorRepository {
  ...

  Future<dynamic> _get(
    Ref ref,
    String path, {
    Map<String, Object?>? queryParameters,
  }) async {
    var user = ref.read(userProvider);
  }
}

    Although here you could pass User user as a parameter to the method and use it inside. But apparently there can be more such dependencies and then it is easier just to pass ref.

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