Rivorpodについての個人的なまとめ

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();
  }
});

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}'),
    );
  }
}

final myAutoDisposeProvider = StateProvider.autoDispose<int>((ref) => 0);
final myFamilyProvider = Provider.family<String, int>((ref, id) => '$id');

final userProvider = FutureProvider.autoDispose.family<User, int>((ref, userId) async {
  return fetchUser(userId);
});

final counterProvider = StateNotifierProvider<Counter, int>((ref) {
  return Counter(ref);
});

class Counter extends StateNotifier<int> {
  Counter(this.ref): super(0);

  final Ref ref;

  void increment() {
    // Counter can use the "ref" to read other providers
    final repository = ref.read(repositoryProvider);
    repository.post('...');
  }
}

class HomeView extends ConsumerWidget {
  const HomeView({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    // use ref to listen to a provider
    final counter = ref.watch(counterProvider);
    return Text('$counter');
  }
}

class HomeView extends ConsumerStatefulWidget {
  const HomeView({super.key});

  @override
  HomeViewState createState() => HomeViewState();
}

class HomeViewState extends ConsumerState<HomeView> {
  @override
  void initState() {
    super.initState();
    // "ref" can be used in all life-cycles of a StatefulWidget.
    ref.read(counterProvider);
  }

  @override
  Widget build(BuildContext context) {
    // We can also use "ref" to listen to a provider inside the build method
    final counter = ref.watch(counterProvider);
    return Text('$counter');
  }
}

class HomeView extends HookConsumerWidget {
  const HomeView({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    // HookConsumerWidget allows using hooks inside the build method
    final state = useState(0);

    // We can also use the ref parameter to listen to providers.
    final counter = ref.watch(counterProvider);
    return Text('$counter');
  }
}

class HomeView extends StatefulHookConsumerWidget {
  const HomeView({super.key});

  @override
  HomeViewState createState() => HomeViewState();
}

class HomeViewState extends ConsumerState<HomeView> {
  @override
  void initState() {
    super.initState();
    // "ref" can be used in all life-cycles of a StatefulWidget.
    ref.read(counterProvider);
  }

  @override
  Widget build(BuildContext context) {
    // Like HookConsumerWidget, we can use hooks inside the builder
    final state = useState(0);

    // We can also use "ref" to listen to a provider inside the build method
    final counter = ref.watch(counterProvider);
    return Text('$counter');
  }
}

Scaffold(
  body: HookConsumer(
    builder: (context, ref, child) {
      // Like HookConsumerWidget, we can use hooks inside the builder
      final state = useState(0);

      // We can also use the ref parameter to listen to providers.
      final counter = ref.watch(counterProvider);
      return Text('$counter');
    },
  ),
);

final filterTypeProvider = StateProvider<FilterType>((ref) => FilterType.none);
final todosProvider = StateNotifierProvider<TodoList, List<Todo>>((ref) => TodoList());

final filteredTodoListProvider = Provider((ref) {
  // obtains both the filter and the list of todos
  final FilterType filter = ref.watch(filterTypeProvider);
  final List<Todo> todos = ref.watch(todosProvider);

  switch (filter) {
    case FilterType.completed:
      // return the completed list of todos
      return todos.where((todo) => todo.isCompleted).toList();
    case FilterType.none:
      // returns the unfiltered list of todos
      return todos;
  }
});

final counterProvider = StateProvider((ref) => 0);

class HomeView extends ConsumerWidget {
  const HomeView({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    // use ref to listen to a provider
    final counter = ref.watch(counterProvider);

    return Text('$counter');
  }
}

final counterProvider = StateNotifierProvider<Counter, int>(Counter.new);

final anotherProvider = Provider((ref) {
  ref.listen<int>(counterProvider, (int? previousCount, int newCount) {
    print('The counter changed $newCount');
  });
  // ...
});

final counterProvider = StateNotifierProvider<Counter, int>(Counter.new);

class HomeView extends ConsumerWidget {
  const HomeView({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    ref.listen<int>(counterProvider, (int? previousCount, int newCount) {
      print('The counter changed $newCount');
    });
    
    return Container();
  }
}

final counterProvider = StateNotifierProvider<Counter, int>(Counter.new);

class HomeView extends ConsumerWidget {
  const HomeView({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // Call `increment()` on the `Counter` class
          ref.read(counterProvider.notifier).increment();
        },
      ),
    );
  }
}

final userProvider = StreamProvider<User>(...);

Widget build(BuildContext context, WidgetRef ref) {
  AsyncValue<User> user = ref.watch(userProvider);

  return user.when(
    loading: () => const CircularProgressIndicator(),
    error: (error, stack) => const Text('Oops'),
    data: (user) => Text(user.name),
  );
}

abstract class User {
  String get name;
  int get age;
}