Bloc: Provide initial value to the BlocBuilder

[ShiinaManatsu]

Want initial value to prevent null state when BlocBuilder fist time built

For multiple page that use the same stream will have a null state when they build first time, and refresh child after bloc updated.

How I fix that for now

The solution now I made is to keep a state last time I updated, and in each widget which will use that bloc will be update in the init() method by the last state in the stream, and next fetch the new state.
This can be used as a "Fake Initial value" to prevent initial null state and I can get visual what data I have so far and don't need to wait for the new fetch

void updateUserBloc() {
  if (userinfo != null) {
    userInfoBloc.update(Future.value(userinfo));
  }

  userInfoBloc.update(memberApi.queryByIdUsingPOST());
}

ResultBase<UserInfo> userinfo;

[Jomik]

What does your UserInfoBloc look like? It sounds like you are not providing it with an initial state?

[ShiinaManatsu]

What does your UserInfoBloc look like? It sounds like you are not providing it with an initial state?

It's basically we have a login screen and it will update the bloc user info and the home widget can show the states. Please have look on the bloc that I basically copy and modified from the examples.

But is the RxBlocBuilder can take an initial value? I don't see that from the implementation.

In each new widget that we may want to update the user info I will call to update it, and without the incoming user info, the RxBlocBuilder will have a null state.

My bloc

abstract class UserInfoBlocEvents {
  void update(Future<ResultBase<UserInfo>> userInfo);
}

abstract class UserInfoBlocStates {
  Stream<ResultBase<UserInfo>> get userinfo;

  @RxBlocIgnoreState()
  Stream<LoginStatus> get isLoggedIn;

  @RxBlocIgnoreState()
  Stream<bool> get isLoading;

  @RxBlocIgnoreState()
  Stream<String> get errors;

  //  We need to keep a token where some method won't return a token
  @RxBlocIgnoreState()
  Stream<UserToken> get userToken;
}

@RxBloc()
class UserInfoBloc extends $UserInfoBloc {
  @override
  Stream<ResultBase<UserInfo>> _mapToUserinfoState() {
    return _$updateEvent
        .switchMap((x) => x.asResultStream())
        .setResultStateHandler(this)
        .whereSuccess();
  }

  @override
  Stream<String> get errors => errorState.skip(1).map((exception) {
        String msg = exception.toString();
        if (msg.contains('Exception:')) msg = msg.replaceAll('Exception:', '');
        return msg;
      });

  @override
  Stream<bool> get isLoading => loadingState;

  @override
  Stream<LoginStatus> get isLoggedIn {
    var stream = states.userinfo.asBroadcastStream();

    var fail = stream
        .where((x) => x?.success == false)
        .switchMap((_) => Future.value(LoginStatus.NotLogin).asStream());

    var success = stream
        .where((x) => x?.success == true && x?.code == 200)
        .where((x) => x?.result != null)
        .where((x) => x?.result?.token != null)
        .switchMap((_) => Future.value(LoginStatus.LoggedIn).asStream());

    return fail.mergeWith([success]).startWith(LoginStatus.NotLogin);
  }

  @override
  Stream<UserToken> get userToken => states.userinfo
      .asBroadcastStream()
      .where((x) => x?.result?.token != null)
      .switchMap((x) => Future.value(x.result.token).asStream());

  /// Closes the [Event] and [State] [Stream]s.
  @mustCallSuper
  void dispose() async {
    await _$updateEvent.drain();
    _$updateEvent.close();
    super.dispose();
  }
}

/// Status determines the application login status
enum LoginStatus { 

How I use the RxBlocBuilder

RxBlocBuilder<UserInfoBlocType, ResultBase<UserInfo>>(
state: (bloc) => bloc.states.userinfo,)

[Jomik]

Hmm, I did not know there was an RxBloc package.
I think you are in the wrong GitHub repo. This is for the Bloc package, https://bloclibrary.dev/.
Are you looking for https://github.com/Prime-Holding/FlutterRxBloc ?

[ShiinaManatsu]

Hmm, I did not know there was an RxBloc package.
I think you are in the wrong GitHub repo. This is for the Bloc package, https://bloclibrary.dev/.
Are you looking for https://github.com/Prime-Holding/FlutterRxBloc ?

Oh god, I'm open an issue at the wrong chrome tab :)
Sorry for the bother~