Read paths: watch, read, and listen.

Provider gives synchronous state. AsyncProvider returns AsyncValue and can expose Future and Stream with strict lifecycle handling.

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Provider Types

Choose provider type by data source and update frequency.

Provider<T>

Synchronous values and local derived state

AsyncProvider<T>

Future/Stream-driven state as AsyncValue<T>

provider.future

Selector that exposes Provider<Future<T>>

Tip

If state comes from network or stream, prefer AsyncProvider first. Keep Provider for pure synchronous logic.

Read API Matrix

Use watch in build paths, read for one-shot access, and listen for 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 and Stream with AsyncProvider

A single AsyncProvider can return a Future or 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, and dispose.

AsyncValue is a sealed class: AsyncLoading / AsyncData / AsyncError.

Pattern matching with switch keeps loading/error UI explicit.

Další kroky

ProviderScope

Move write operations into provider methods and execute via ref.invoke.

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Čtení providerů

Choose between Consumer, ConsumerWidget, and ConsumerStatefulWidget.

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