Storage

The quickest way to persist queries is to use Cached Storage. But you can also easily implement your own.

CachedStorage

Cached Storage is built upon Sqflite as this allows simple asyncronus access to a database.

Getting Started

Initialized cached query with the storage interface. This must be initialized before any query is called.

void main() async {
  CachedQuery.instance.configFlutter(
    storage: await CachedStorage.ensureInitialized(),
  );
}

Queries will then automatically be persisted.

Serialization

Cached Storage uses jsonEncode to convert the data of a query to json, which is then stored. If you are returning dart objects from the queryFn you will need to serialized the json back into the dart object. To do this, pass a serilizer to the QueryConfig which will be used to turn the stored data back into a dart object.

Query<JokeModel>(
  key: 'joke',
  config: QueryConfig(
    // Use a deserializer to transform the stored json to an object.
    storageDeserializer: (dynamic json) =>
        JokeModel.fromJson(json as Map<String, dynamic>),
  ),
  queryFn: () async {
    final req = client.get(
      Uri.parse("https://icanhazdadjoke.com/"),
      headers: {"Accept": "application/json"},
    );
    final res = await req;
    return JokeModel.fromJson(
        jsonDecode(res.body) as Map<String, dynamic>,
    );
  },
);

Custom Storage

There is no need to depend on Cached Storage if you are implementing a custom solution. To get started using a custom storage solution extend StorageInterface from Cached Query, shown below.

/// An interface for any storage adapter.
///
/// Used by the [CachedStorage] plugin to save the current cache.
abstract class StorageInterface {
  /// Get stored data from the storage instance.
  FutureOr<dynamic> get(String key);

  /// Delete the cache at a given key.
  void delete(String key);

  /// Update or add data with a given key.
  /// Item will be the data from a Query or Infinite Query
  void put<T>(String key, {required T item});

  /// Delete all stored data.
  void deleteAll();

  /// Close and clean up the storage instance.
  void close();
}

For a further example of implementing the storage interface look at the source code for Cached Storage: Source Code