majiayu000 Riverpod — Family
Instructions
Family lets a single provider have multiple independent states, one per parameter combination (like a Map from parameter to state). Use it for API calls that depend on an ID, query, or page number.
Creating a family (functional)
Add .family and an extra type parameter for the argument. The provider function receives (ref, param):
final userProvider = FutureProvider.autoDispose.family<User, String>((ref, id) async {
final dio = Dio();
final response = await dio.get('https://api.example.com/users/$id');
return User.fromJson(response.data);
});
With code generation, add parameters to the function; the generated provider accepts arguments: userProvider(id).
Creating a family (Notifier)
Use NotifierProvider.family / AsyncNotifierProvider.family (and .autoDispose.family). The Notifier must have a constructor that stores the parameter:
final userProvider = AsyncNotifierProvider.autoDispose.family<UserNotifier, User, String>(
UserNotifier.new,
);
class UserNotifier extends AsyncNotifier<User> {
UserNotifier(this.id);
final String id;
@override
Future<User> build() async {
final dio = Dio();
final response = await dio.get('https://api.example.com/users/$id');
return User.fromJson(response.data);
}
}
Using a family
Pass the parameter when watching or reading:
final user = ref.watch(userProvider('123'));
final other = ref.watch(userProvider('456')); // independent state
Parameters must have consistent == and hashCode. Do not use mutable or list/map literals as parameters (e.g. ref.watch(myProvider([1,2,3])) is wrong because [1,2,3] != [1,2,3]). Prefer primitives or custom classes with ==/hashCode. Enable riverpod_lint provider_parameters rule to catch mistakes.
Auto-dispose with family
Enable auto-dispose when using family so that when the parameter goes out of use (e.g. user navigates away), that parameter's state can be disposed and you avoid unbounded cache growth.
Overriding in tests
- Override a single parameter: pass the same parameter to the override.
- Override all parameters: override with a provider that ignores the parameter or returns a fixed value. See riverpod-overrides and the docs for exact syntax.