块迁移后的问题 - 在事件处理程序正常完成后调用发出

Question

在我迁移到最新版本的 bloc 后，我遇到了错误。 这是我迁移前的代码：

  SignInBloc(
      {required this.authenticationRepository,
      required this.userDataRepository})
      : super(SignInInitialState());

  SignInState get initialState => SignInInitialState();

  @override
  Stream<SignInState> mapEventToState(
    SignInEvent event,
  ) async* {
    if (event is SignInWithGoogle) {
      yield* mapSignInWithGoogleToState();
    }
    if (event is UpdateLastLoginEvent) {
      yield* mapUpdateLastLoginEventToState(event.uid, event.deviceID);
    }
  }

  Stream<SignInState> mapSignInWithGoogleToState() async* {
    yield SignInWithGoogleInProgressState();
    try {
      String res = await authenticationRepository.signInWithGoogle();
      yield SignInWithGoogleCompletedState(res);
    } catch (e) {
      print(e);
      yield SignInWithGoogleFailedState();
    }
  }

  Stream<SignInState> mapUpdateLastLoginEventToState(
      String uid, String deviceID) async* {
    yield UpdateLastLoginInProgressState();
    try {
      String? res = await userDataRepository.lastLogin(uid, deviceID);
      if (res != null) {
        yield UpdateLastLoginCompletedState(res);
      } else {
        yield UpdateLastLoginFailedState();
      }
    } catch (e) {
      print(e);
      yield UpdateLastLoginFailedState();
    }
  }

这是我在迁移后为代码所做的。虽然我不确定用 try 编码是否仍然是一件好事。

  SignInBloc(
      {required this.authenticationRepository,
      required this.userDataRepository})
      : super(SignInInitialState()) {
    on<SignInEvent>((event, emit) async {
      if (event is SignInWithGoogle) {
        mapSignInWithGoogleToState(emit);
      }
      if (event is UpdateLastLoginEvent) {
        mapUpdateLastLoginEventToState(emit, event.uid, event.deviceID);
      }
    });
  }

  Future<void> mapSignInWithGoogleToState(
    Emitter<SignInState> emit,
  ) async {
    emit(SignInWithGoogleInProgressState());
    try {
      String res = await authenticationRepository.signInWithGoogle();
      emit(SignInWithGoogleCompletedState(res));
    } catch (e) {
      print(e);
      emit(SignInWithGoogleFailedState());
    }
  }

  Future<void> mapUpdateLastLoginEventToState(
    Emitter<SignInState> emit,
    String uid,
    String deviceID,
  ) async {
    emit(UpdateLastLoginInProgressState());
    try {
      String? res = await userDataRepository.lastLogin(uid, deviceID);
      if (res != null) {
        emit(UpdateLastLoginCompletedState(res));
      } else {
        emit(UpdateLastLoginFailedState());
      }
    } catch (e) {
      print(e);
      emit(UpdateLastLoginFailedState());
    }
  }

这是我在日志中看到的内容，但如果我尝试实现 future.whenComplete，则会出现语法错误。请帮忙。谢谢！

I/flutter (18083): emit was called after an event handler completed normally.
I/flutter (18083): This is usually due to an unawaited future in an event handler.
I/flutter (18083): Please make sure to await all asynchronous operations with event handlers
I/flutter (18083): and use emit.isDone after asynchronous operations before calling emit() to
I/flutter (18083): ensure the event handler has not completed.
I/flutter (18083): 
I/flutter (18083):   **BAD**
I/flutter (18083):   on<Event>((event, emit) {
I/flutter (18083):     future.whenComplete(() => emit(...));
I/flutter (18083):   });
I/flutter (18083): 
I/flutter (18083):   **GOOD**
I/flutter (18083):   on<Event>((event, emit) async {
I/flutter (18083):     await future.whenComplete(() => emit(...));
I/flutter (18083):   });

Answer 1

请尝试如下调整：

SignInBloc(
      {required this.authenticationRepository,
      required this.userDataRepository})
      : super(SignInInitialState()) {

    // change this
    /*on<SignInEvent>((event, emit) {
      if (event is SignInWithGoogle) {
        mapSignInWithGoogleToState(emit);
      }
      if (event is UpdateLastLoginEvent) {
        mapUpdateLastLoginEventToState(emit, event.uid, event.deviceID);
      }
    });*/

    // to this
    on<SignInWithGoogle>(mapSignInWithGoogleToState);
    on<UpdateLastLoginEvent>(mapUpdateLastLoginEventToState);
  }

同时调整你的功能：

Future<void> mapSignInWithGoogleToState(
    SignInWithGoogle event,
    Emitter<SignInState> emit,
  ) async {
...
}

Future<void> mapUpdateLastLoginEventToState(
    UpdateLastLoginEvent event,
    Emitter<SignInState> emit,
  ) async {
...
}

使用 try/catch 方法还是可以的！

如果有效，请告诉我。