init method
Required called before all to load
Implementation
Future<void> init() async {
this.lastPrefix ??= defaultPrefix;
_languageDb.sink.add(
(await FirebaseDatabase.instance.ref().child(child).once())
.snapshot
.value as dynamic);
FirebaseDatabase.instance
.ref()
.child(child)
.onValue
.listen((v) => _languageDb.sink.add(v.snapshot.value as dynamic));
_languageDb.listen((v) => _languageList.sink.add(v[lastPrefix]));
await _setDeviceLanguage();
}