Providers
Provider gives synchronous state. AsyncProvider returns AsyncValue et can expose Future et Stream avec strict lifecycle handling.
Provider types
Choose provider type by data source et update frequency.
Provider<T>
Synchronous values et local derived state
AsyncProvider<T>
Future/Stream-driven state as AsyncValue<T>
provider.future
Selector that exposes Provider<Future<T>>
Tip
If state comes de network ou stream, prefer AsyncProvider first. Keep Provider pour pure synchronous logic.
Read API Matrix
Use watch dans build paths, read pour one-shot access, et listen pour side effects.
Most common
final value = ref.watch(myProvider);
watch / read / listen
ref.watch(provider) : subscribe and rebuild when value changes.
ref.read(provider) : read current snapshot without subscribing.
container.listen(...) : callback-driven updates; optional fireImmediately.
Future et Stream avec AsyncProvider
A single AsyncProvider can return a Future ou bind a Stream via ref.emit(stream).
user_sources.dart
final currentUser = AsyncProvider<User>((ref) async {
final api = ref.watch(apiProvider);
return api.me();
});
final liveUser = AsyncProvider<User>((ref) {
final stream = ref.watch(apiProvider).live();
ref.emit(stream);
return const User(name: 'Loading...');
}, autoDispose: true, autoDisposeDelay: const Duration(milliseconds: 250));
// Await as Future
final user = await ref.watch(currentUser.future);
ref.emit(stream) cancels prior subscription on rebuild, invalidate, et dispose.
AsyncValue is a sealed class: AsyncLoading / AsyncData / AsyncError.
Pattern matching avec switch keeps loading/error UI explicit.