Declarative programming

Write business logic in a manner similar to Stateless widgets.
Have your network requests to automatically recompute when necessary and make your logic easily reusable/composable/maintainable.

Easily implement common UI patterns

Using Riverpod, common yet complex UI patterns such as "pull to refresh"/ "search as we type"/etc... are only a few lines of code away.

Tooling ready

Riverpod enhances the compiler by having common mistakes be a compilation-error. It also provides custom lint rules and refactoring options. It even has a command line for generating docs.

Features

✅ Declarative programming
✅ Native network requests support
✅ Automatic loading/error handling
✅ Compile safety
✅ Type-safe query parameters
✅ Test ready
✅ Work in plain Dart (servers/CLI/...)
✅ Easily combinable states
✅ Built-in support for pull-to-refresh
✅ Custom lint rules
✅ Built-in refactorings
✅ Hot-reload support
✅ Logging
✅ Websocket support
✅ Documentation generator

任意位置声明共享状态

不再需要在你的 main.dart 和UI文件之间来回跳转。
将共享状态的代码放在它所属的位置上，无论是放在独立的package中还是放在需要它的Widget旁边，都不会丢失它的可测试性。

// A shared state that can be accessed by multiple
// objects at the same time
final countProvider = StateProvider((ref) => 0);

// Consumes the shared state and rebuild when it changes
class Title extends ConsumerWidget {
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final count = ref.watch(countProvider);
    return Text('$count');
  }
}

最小粒度更新UI和重新计算状态

我们无需在 build 中对列表进行排序或过滤，也不必依赖高级的缓存机制。

使用 Provider 和 "families" 修饰符，那么它只会在你真正需要的时候才发起HTTP请求或整理你的列表。

final todosProvider = StateProvider<List<Todo>>((ref) => []);
final filterProvider = StateProvider<Filter>((ref) => Filter.all);

final filteredTodosProvider = Provider<List<Todo>>((ref) {
  final todos = ref.watch(todosProvider);
  switch (ref.watch(filterProvider)) {
    case Filter.all:
      return todos;
    case Filter.completed:
      return todos.where((todo) => todo.completed).toList();
    case Filter.uncompleted:
      return todos.where((todo) => !todo.completed).toList();
  }
});

Simplify day-to-day work with refactors

Riverpod offers various refactors, such as "Wrap widget in a Consumer" and many more. See the list of refactorings.

Keep your code maintainable with lint rules

New lint-rules specific to Riverpod are implemented and more are continuously added. This ensures your code stays in the best conditions. See the list of lint rules.

安全使用Provider

使用provider不再导致错误的状态。恰当地使用provider，你可以始终获得一个可靠的结果。

这在异步操作中也是如此，Riverpod可以让你简洁地处理loading/error状态。

final configurationsProvider = FutureProvider<Configuration>((ref) async {
  final uri = Uri.parse('configs.json');
  final rawJson = await File.fromUri(uri).readAsString();

  return Configuration.fromJson(json.decode(rawJson));
});

class Example extends ConsumerWidget {
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final configs = ref.watch(configurationsProvider);

    // Use Riverpod's built-in support
    // for error/loading states using "when":
    return configs.when(
      loading: () => const CircularProgressIndicator(),
      error: (err, stack) => Text('Error $err'),
      data: (configs) => Text('data: ${configs.host}'),
    );
  }
}

在DevTools中检查状态

你可以在Flutter的开发工具中一目了然地看到Riverpod的各种状态。
此外，一款功能更全面的状态检查工具正在开发中。