Initialize a store the first time is created in sembast - database

Question

I'm developing a mobile application in Flutter, and I would like to manage the settings of my application (light theme or dark theme, ...).
I'm using sembast to store the settings of my application. I would like to initialize the store with some initial values the first time is created. How can I do that?
This is the my database helper class:
class AppDatabase {
// Name of the database.
static final String _dbName = 'mydb.db';
// Singleton instance.
static final AppDatabase _singleton = AppDatabase._();
// Singleton getter.
static AppDatabase get instance => _singleton;
// Transforms synchronous code into asynchronous code.
Completer<Database> _dbOpenCompleter;
// Private constructor.
AppDatabase._();
// Database object getter.
Future<Database> get database async {
// If completer is null, AppDatabaseClass is newly instantiated, so database is not yet opened.
if (_dbOpenCompleter == null) {
_dbOpenCompleter = Completer();
_openDatabase();
}
return _dbOpenCompleter.future;
}
Future<void> _openDatabase() async {
// Get a platform-specific directory where persistent app data can be stored.
final appDocumentDir = await getApplicationDocumentsDirectory();
// Path with the form: /platform-specific-directory/demo.db
final dbPath = join(appDocumentDir.path, _dbName);
final database = await databaseFactoryIo.openDatabase(dbPath);
// Any code awaiting the Completer's future will now start executing.
_dbOpenCompleter.complete(database);
}
}
Then I use the following repository to perform CRUD operations on my Settings:
class SettingsDatabaseRepository implements SettingsRepository {
// The name of the store.
static const String SETTINGS_STORE_NAME = 'settings';
// This store acts like a persistent map, values of which are Settings objects
// converted to Map.
final _settingsStore = intMapStoreFactory.store(SETTINGS_STORE_NAME);
// Private getter to shorten the amount of code needed to get the singleton
// instance of an opened database.
Future<Database> get _db async => await AppDatabase.instance.database;
#override
Future<void> insert(Settings settings) async {
await _settingsStore.add(await _db, settings.toMap());
}
#override
Future<void> update(Settings settings) async {
final finder = Finder(filter: Filter.byKey(settings.settingsId));
await _settingsStore.update(
await _db,
settings.toMap(),
finder: finder,
);
}
#override
Future<Settings> getSettings() async {
final recordSnapshots = await _settingsStore.find(await _db);
final settingsList = recordSnapshots.map((snapshot) {
final settings = Settings.fromMap(snapshot.value);
settings.copyWith(settingsId: snapshot.key);
return settings;
}).toList();
if (settingsList.isEmpty)
return null;
else
return settingsList.first;
}
}

Answer 1

I would like to initialize the store with some initial values the first time is created.
You cannot perform action when a store is created (since a store is not really created, it just holds records), however you can perform action when the database is created.
Sembast supports a database versioning system similar to sqlite, although here there is not much schema to modify. You can use this system to perform action when the database is created (or when you decide later in a new version to update it).
// Our shop store sample data
var store = intMapStoreFactory.store('shop');
var db = await factory.openDatabase(path, version: 1,
onVersionChanged: (db, oldVersion, newVersion) async {
// If the db does not exist, create some data
if (oldVersion == 0) {
await store.add(db, {'name': 'Lamp', 'price': 10});
await store.add(db, {'name': 'Chair', 'price': 15});
}
});
See more info