I'm using a custom made State class to store result but seems compiler is complaining about the diff...

# coroutines

[flamy]

I'm using a custom made State class to store result but seems compiler is complaining about the different types
Does anyone know any workaround for this?

Code in 🧵

[flamy]

sealed interface UiState<out T> {
    data class Success<T>(val value: T) : UiState<T>
    data class Error(val exception: Throwable? = null, val message: String = ""): UiState<Nothing>
    data object Loading : UiState<Nothing>
}

val currentPathFiles: StateFlow<UiState<List<File>>> = currentPath
        .filterNotNull()
        .flowOn(<http://dispatcher.io|dispatcher.io>())
        .flatMapLatest { directoryProvider.observeDir(it) }
        .map { UiState.Success(it) }
        .catch { emit(UiState.Error(it)) }
        .toStateFlow(initialState = UiState.Loading)

[Dmitry Khalanskiy [JB]]

Try

.map { UiState.Success(it) as UiState<List<File>> }

Otherwise, map thinks that the new flow type must be UiState.Success, as that's the most specific type it can infer. You can let it know that you want a less specific type.

[flamy]

@Dmitry Khalanskiy [JB] it works, but IDE thinks it's a useless cast 🫠

[Chrimaeon]

it in catch is a exception so you are not emitting a UIState with list as declared in the return type

[Rok Oblak]

you can also specify the generic type at that map call to make it clear you want UIState and not UIState.Success, otherwise it will infer the most specific type at that point which is Success

[ephemient]

btw you can do either of

.map<_, UiState<List<File>>> { UiState.Success(it) }
.catch { emit(UiState.Error(it)) }

or

.map { UiState.Success(it) }
.catch<UiState<List<File>>> { UiState.Error(it) }

which avoids as