riverpod-scoping（Riverpod 范围界定）

Riverpod — Scoping providers

Instructions

Scoping means changing a provider's behavior for only part of the app by overriding it in a non-root ProviderScope. Use cases: page-specific customization (e.g. theme for one page), performance (e.g. rebuild only the item that changed in a ListView), or avoiding passing family parameters through the tree.

Note: Scoping is complex and may be reworked in future Riverpod versions. Use with care.

Opt-in: dependencies

By default you cannot scope a provider. Opt in by setting dependencies on the provider. The first scoped provider usually has dependencies: const [].

final currentItemIdProvider = Provider<String?>(
  dependencies: const [],
  (ref) => null,
);

Listening to a scoped provider

Use ref.watch/ref.read as usual. If another provider listens to a scoped provider, that listening provider must list the scoped provider in its dependencies:

final currentItemProvider = FutureProvider<Item?>(
  dependencies: [currentItemIdProvider],
  (ref) async {
    final currentItemId = ref.watch(currentItemIdProvider);
    if (currentItemId == null) return null;
    return fetchItem(id: currentItemId);
  },
);

Only scoped providers need to be listed in dependencies; non-scoped providers do not.

Setting the scoped value: overrides

Use overrides on a ProviderScope that wraps the subtree where the scoped value should apply:

ProviderScope(
  overrides: [
    currentItemIdProvider.overrideWithValue('123'),
  ],
  child: const DetailPageView(),
)

That way the detail page sees '123' as the current item ID without it being passed down manually. See riverpod-overrides for override syntax.