使用 bloc 保持存储库实例“活着”

Question

I am still with my first bloc based app, adding features. While previously, I stored some of my page specific data with the bloc class, for the last feature, I now moved most variables into its repository. I already feared that the instance of calling the repository gets lost, afterwards, which now proved true.

Is there a proper, easy way to make the instance persistent?

I know of inherited widgets, however, I have not yet figured out how to implement this and my question around this unfortunately remained unanswered. It would be great, if someone could point me to some direction!

In general, my idea was to have the api dealing with local files and online data, the repository with frequently re-used data (session data, presented data etc) and helper variables within the bloc. So when the UI requests data, the bloc asks the repository which will either return a value stored in a variable or request a value from the api.

This is, how the strucuture basically looks like (hope I have not missed anything significant)

void main() async {
  final UserRepository userRepository = UserRepository(); // <===== userRepository initialized
  runApp(MyApp(userRepository: UserRepository()));
}

class MyApp extends StatelessWidget {
  MyApp({Key key, this.userRepository}) : assert(userRepository != null), super(key: key);
  final UserRepository userRepository;

  @override
  Widget build(BuildContext context) {
    return BlocProvider<UserBloc>(  <====== userBloc injection to top of widget tree 
      create: (_) => UserBloc(userRepository: userRepository)..add(AppStarted()),
      child: App(),
    );
  }
}
// =================================================== APP WITH ROUTES
class App extends StatelessWidget {
  App({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return CupertinoApp(
      routes: {
        '/': (_) => HomePage(),
        'feature 1': (_) => HomePage(),
      },
    );
  }
}
// =================================================== LANDING PAGE WITH MAIN MENU
class HomePage extends StatefulWidget {
  HomePage({Key key, this.title}) : super(key: key);
  final String title;
  @override
  _HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage>  { 
  @override
  Widget build(BuildContext context) {
    SystemChrome.setPreferredOrientations([
      DeviceOrientation.portraitUp,
    ]);
    return CupertinoPageScaffold(
      navigationBar: CupertinoNavigationBar(
        middle: Text('MathUup'),
      ),
      child: SafeArea(
        child: CupertinoButton(
          child: Text('Feature 1',
              onPressed: () => Navigator.pushNamed(context, 'feature 1'),
  ),)));
}}     
// =================================================== BLOC
class UserBloc extends Bloc<UserEvent, UserState> {
  UserBloc({this.userRepository}) : super(AppInitial());
  final UserRepository userRepository;
  ...
    
      final user = await userRepository.getActiveUserData(userId);
      final lastSessionData = await userRepository.getLastSession(userId);
  ...
}
// =================================================== REPOSITORY
class UserRepository {
  UserRepository();
  final UserApiClient achievementsApiClient = UserApiClient();
  final SessionsApiClient sessionsApiClient = SessionsApiClient();
  UserSession activeUserSession;
  User activeUserData;
  
  
  Future<String> getLastUserId() async {
    final lastUserId = await sessionsApiClient.getLastUserId();
    return lastUserId;
  }
  Future<UserSession> getActiveUser() async {
    if (activeUserSession == null) {
      activeUserSession = await sessionsApiClient.getLastUser();
    }
    return activeUserSession;
  }
}
  
  

Answer 1

This line is creating and initializing your user repository:

final UserRepository userRepository = UserRepository(); // <===== userRepository initialized

However, this line is not passing that repository, it's creating a new repository, ignoring the one you just initialized:

runApp(MyApp(userRepository: UserRepository()));

I think you meant to use the variable you already have:

runApp(MyApp(userRepository: userRepository));