chetan2921/flo/riverpod-offline

Riverpod — Offline persistence (experimental)

Instructions

Offline persistence stores provider state on device so it survives restarts and works offline. Riverpod is storage-agnostic; packages like riverpod_sqflite provide a Storage implementation. Only Notifier-based providers can be persisted. The feature is experimental.

Creating a Storage

Install a package (e.g. riverpod_sqflite + sqflite) and create a Storage. With SQFlite:

final storageProvider = FutureProvider<Storage<String, String>>((ref) async {
  return JsonSqFliteStorage.open(
    join(await getDatabasesPath(), 'riverpod.db'),
  );
});

Persisting a notifier

Inside the notifier's build, call persist with: the Storage (e.g. ref.watch(storageProvider.future)), a unique key, and encode/ decode for your state. Do not await persist; Riverpod handles it.

class TodoList extends AsyncNotifier<List<Todo>> {
  @override
  Future<List<Todo>> build() async {
    persist(
      ref.watch(storageProvider.future),
      key: 'todo_list',
      encode: (todos) => todos.map((todo) => {'task': todo.task}).toList(),
      decode: (json) => (json as List).map((todo) => Todo(task: todo['task'] as String)).toList(),
    );
    return fetchTodosFromServer();
  }
}

Keys

• Unique across all persisted providers (same key = same row, risk of corruption).
• Stable across restarts (changing the key loses restored state).
• For family providers, include the parameter in the key.

JsonPersist (code generation)

With riverpod_sqflite and codegen, use @JsonPersist() so key/encode/decode are generated:

@riverpod
@JsonPersist()
class TodoList extends _$TodoList {
  @override
  Future<List<Todo>> build() async {
    persist(ref.watch(storageProvider.future));
    return fetchTodosFromServer();
  }
}

Cache duration

By default state is cached for a short time (e.g. 2 days). For long-lived data (e.g. user preferences), set StorageOptions:

persist(
  ref.watch(storageProvider.future),
  options: const StorageOptions(cacheTime: StorageCacheTime.unsafe_forever),
  // ...
);

If using forever, plan to delete or migrate data when the app changes; Riverpod does not do migrations.

Destroy key (simple migration)

When the data shape changes, use destroyKey so old data is discarded:

options: const StorageOptions(destroyKey: '1.0'),

Bump the string in new releases; old persisted state is then ignored and the provider starts fresh.

Waiting for decode

To initialize from persisted state instead of a network call, await the persist future:

await persist(ref.watch(storageProvider.future), key: 'todo_list', ...).future;
return state.value ?? <Todo>[];

Testing

Override the storage provider with Storage.inMemory() so tests don't need a real database:

ProviderScope(
  overrides: [
    storageProvider.overrideWith((ref) => Storage<String, String>.inMemory()),
  ],
  child: const MyApp(),
)

For advanced migrations or custom storage strategies, you may still need to work with the database directly.