无法使用异步接收的数据更新 BLoC 状态

Question

我将在 firebase 商店中创建 Photo 实体，我需要获取两个字段，例如当前用户的电子邮件和 Photo url，但我的 BLoC 不会使用异步接收的数据更新状态。这是我的代码

  saved: (e) async* {
    Either<PhotoFailure, Unit> failureOrSuccess;
    final userOption = await _authFacade.getSignedInUser();
    final user = userOption.fold(() => null, (user) => user);
    print(user.emailAddress.getOrCrash());
    yield state.copyWith(
        photo:
            state.photo.copyWith(author: user.emailAddress.getOrCrash()));
    print(state.photo.author);
    yield state.copyWith(
        photo: state.photo.copyWith(
            uploadDate: DateFormat("dd-MM-yyyy").format(DateTime.now())));
    print(state.photo.uploadDate);
    FirebaseStorage _storage = FirebaseStorage.instance;
    Reference _rootReference = _storage.ref().child('photos');
    UploadTask task = _rootReference.putFile(state.photoFile);
    String downloadUrl = await (await task).ref.getDownloadURL();
    print(downloadUrl);
    yield state.copyWith(
      photo: state.photo.copyWith(url: downloadUrl),
    );
    print(state.photo.url);

    yield state.copyWith(
      isSaving: true,
      saveFailureOrSuccessOption: none(),
    );

    if (state.photo.failureOption.isNone()) {
      state.isEditing
          ? await _photoRepository.update(state.photo)
          : await _photoRepository.create(state.photo);
    }

    yield state.copyWith(
      isSaving: false,
      showErrorMessages: AutovalidateMode.always,
      saveFailureOrSuccessOption: optionOf(failureOrSuccess),
    );
  },
);

}

如您所见，我决定打印所有结果并在控制台记录此

I/flutter (19212): test@gmail.com
I/flutter (19212): 
I/flutter (19212): 2021-01-07 16:47:23.279989
D/UploadTask(19212): Increasing chunk size to 524288
I/flutter (19212): https://firebasestorage.googleapis.com/v0/b/simplefirebasegalley.appspot.com/o/photos?alt=media&token=73b3537f-d36c-49a8-b080-5cd27837c50e
I/flutter (19212):

所以我得到了正确的数据，但我不能只用异步数据更新状态，因为 uploadDate 工作正常。

我的州代码

@freezed
 abstract class PhotoFormState with _$PhotoFormState {
   const factory PhotoFormState({
     @required Photo photo,
     @nullable @required File photoFile,
     @required AutovalidateMode showErrorMessages,
     @required bool isEditing,
     @required bool isSaving,
     @required Option<Either<PhotoFailure, Unit>> saveFailureOrSuccessOption,
     }) = _PhotoFormState;

   factory PhotoFormState.initial() => PhotoFormState(
       photo: Photo.empty(),
       photoFile: null,
       showErrorMessages: AutovalidateMode.disabled,
       isEditing: false,
       isSaving: false,
       saveFailureOrSuccessOption: none(),
       );
 }

这是我的照片实体类

@freezed
 abstract class Photo with _$Photo {
   const Photo._();

   const factory Photo({
     @required String url,
     @required String type,
     @required int watchCount,
     @required UniqueId id,
     @required PhotoName name,
     @required PhotoDescription description,
     @required TagList<Tag> tagList,
     @required String author,
     @required String uploadDate,
     @required FieldValue serverTimeStamp,
   }) = _Photo;

   factory Photo.empty() => Photo(
         url: '',
         type: 'new',
         id: UniqueId(),
         name: PhotoName(''),
         description: PhotoDescription(''),
         tagList: TagList(new List()),
         watchCount: 0,
         author: '',
         serverTimeStamp: FieldValue.serverTimestamp(),
         uploadDate: DateTime.now().toString(),
       );

   Option<ValueFailure<dynamic>> get failureOption {
     return name.failureOrUnit
         .andThen(description.failureOrUnit)
         .andThen(tagList.failureOrUnit)
         .fold((f) => some(f), (r) => none());
   }
 }

Answer 1

如果我没看错，您使用 .copyWith 会多次产生相同的状态。但是，为了更新 UI，您需要发送间歇状态。所以通常你会

yield myDisplayState(); yield inProgress(); yield myDisplayState(); yield inProgress(); yield myDisplayState();

如果您之间没有其他状态，您将在 UI 上看到没有变化