I'm trying to catch any error cases in the ViewModel and update the UIState, but it's not working.

This is the sealed interface to handle the different responses:

sealed interface UniversalisUiState {
    data object Loading : UniversalisUiState

    data class UniversalisData(
        val selectedTopicId: String,
        val topics: UniversalisResource,
    ) : UniversalisUiState

    data object Empty : UniversalisUiState

    data class UniversalisError(
        val message: String,
    ) : UniversalisUiState

}

In the ViewModel the relevant code is:

val uiState: StateFlow<UniversalisUiState> = combine(
    selectedTopicId,
    getUniversalisUseCase.invoke(
        date = selectedDate.value,
        title = route.initialTopicId!!,
        selectedTopicId = LiturgyHelper.liturgyByName(route.initialTopicId!!)
            .toString()
    ).catch {
        //NOT WORKING *******
        //emit(UniversalisUiState.UniversalisError(it.message))
        Timber.d("aaa", it.message)
    },
    UniversalisUiState::UniversalisData,
).stateIn(
    scope = viewModelScope,
    started = SharingStarted.WhileSubscribed(5_000),
    initialValue = Loading,
)

And in the UseCase:

class GetUniversalisUseCase @Inject constructor(
    private val universalisRepository: UniversalisRepository,
    private val userDataRepository: UserDataRepository,
) {

    operator fun invoke(
        date: Int,
        selectedTopicId: String,
        title: String
    ): Flow<UniversalisResource>
    {
        return combine(
            userDataRepository.userData,
            universalisRepository.getUniversalisByDate(
                UniversalisResourceQuery(
                    filterDate = date,
                    selectedTopic = selectedTopicId.toInt()
                )
            ),
        ) { userData, universalis ->
            if (universalis.todayDate == 0 && selectedTopicId != "30") {
                universalisRepository.insertFromRemote(
                    UniversalisResourceQuery(
                        date,
                        selectedTopicId.toInt()
                    )
                )
            }
            UniversalisResource(
                date = universalis.todayDate, 
                title = title,
                name = "",
                id = selectedTopicId.toInt(),
                data = universalis,
                dynamic = userData
            )
        }
    }
}

How I can do this: emit(UniversalisUiState.UniversalisError(it.message)) when catching errors? I can see de error of Timber, but I can't emit UniversalisError.

I'm trying to catch any error cases in the ViewModel and update the UIState, but it's not working.

This is the sealed interface to handle the different responses:

sealed interface UniversalisUiState {
    data object Loading : UniversalisUiState

    data class UniversalisData(
        val selectedTopicId: String,
        val topics: UniversalisResource,
    ) : UniversalisUiState

    data object Empty : UniversalisUiState

    data class UniversalisError(
        val message: String,
    ) : UniversalisUiState

}

In the ViewModel the relevant code is:

val uiState: StateFlow<UniversalisUiState> = combine(
    selectedTopicId,
    getUniversalisUseCase.invoke(
        date = selectedDate.value,
        title = route.initialTopicId!!,
        selectedTopicId = LiturgyHelper.liturgyByName(route.initialTopicId!!)
            .toString()
    ).catch {
        //NOT WORKING *******
        //emit(UniversalisUiState.UniversalisError(it.message))
        Timber.d("aaa", it.message)
    },
    UniversalisUiState::UniversalisData,
).stateIn(
    scope = viewModelScope,
    started = SharingStarted.WhileSubscribed(5_000),
    initialValue = Loading,
)

And in the UseCase:

class GetUniversalisUseCase @Inject constructor(
    private val universalisRepository: UniversalisRepository,
    private val userDataRepository: UserDataRepository,
) {

    operator fun invoke(
        date: Int,
        selectedTopicId: String,
        title: String
    ): Flow<UniversalisResource>
    {
        return combine(
            userDataRepository.userData,
            universalisRepository.getUniversalisByDate(
                UniversalisResourceQuery(
                    filterDate = date,
                    selectedTopic = selectedTopicId.toInt()
                )
            ),
        ) { userData, universalis ->
            if (universalis.todayDate == 0 && selectedTopicId != "30") {
                universalisRepository.insertFromRemote(
                    UniversalisResourceQuery(
                        date,
                        selectedTopicId.toInt()
                    )
                )
            }
            UniversalisResource(
                date = universalis.todayDate, 
                title = title,
                name = "",
                id = selectedTopicId.toInt(),
                data = universalis,
                dynamic = userData
            )
        }
    }
}

How I can do this: emit(UniversalisUiState.UniversalisError(it.message)) when catching errors? I can see de error of Timber, but I can't emit UniversalisError.

• kotlin
• kotlin-coroutines
• clean-architecture

1 Answer 1

Since you want to emit a UniversalisUiState, you need to move the catch after the combine, when the flow is already of that type:

val uiState: StateFlow<UniversalisUiState> = combine(
    selectedTopicId,
    getUniversalisUseCase.invoke(
        date = selectedDate.value,
        title = route.initialTopicId!!,
        selectedTopicId = LiturgyHelper.liturgyByName(route.initialTopicId!!)
            .toString()
    ),
    UniversalisUiState::UniversalisData,
).catch<UniversalisUiState> {
    emit(UniversalisUiState.UniversalisError(it.message))
    Timber.d("aaa", it.message)
}.stateIn(
    scope = viewModelScope,
    started = SharingStarted.WhileSubscribed(5_000),
    initialValue = UniversalisUiState.Loading,
)

You might need to explicitly specify the interface UniversalisUiState as the generic type of catch, so Kotlin can correctly infer the type of the resulting flow.