Is there any recommendation to handle UI as State ...

# compose

[Lucien Guimaraes]

Is there any recommendation to handle UI as State ? I currently have a Flow<UIState>, UIState being a sealed class. In my Screen with a when(uiState) depending of the value I display different Composable. The thing is, I crash when a different value is pushed (for example Loading -> Success is fine, but Success -> Error I crash). Any idea why ? 🤔 Code is in thread

[Lucien Guimaraes]

inside my ViewModel:

sealed class HomeUIState {
    object Loading : HomeUIState()
    data class Error(val homeErrorConfiguration: HomeErrorConfiguration) : HomeUIState()
    data class Explore(val sectionList: List<Section>) : HomeUIState()
}

val uiState: Flow<HomeUIState> = homeInteractor.homeState.map { //map the result from what the business logic class is doing (call to repository and stuff) to an uiState}

inside my Composable Screen:

val uiState by homeViewModel.uiState.collectAsState(HomeUIState.Loading)
when (uiState) {   
   is HomeUIState.Error -> { //Displaying Error Screen}
   is HomeUIState.Explore -> { //Displaying "success" screen}
   else -> { //Displaying loading screen }
}

When opening the app it's working fine. I have the Loading -> Error or Loading -> Explore, but if a new event is trigger the app crash because inside the composable screen it's doing a cast inside the wrong switch.

[brandonmcansh]

val viewState by rememberFlowWithLifecycle(viewModel.state)
    .collectAsState(initial = PhotoDiscoveryViewState.Empty)

[brandonmcansh]

@Composable
fun <T> rememberFlowWithLifecycle(
    flow: Flow<T>,
    lifecycle: Lifecycle = LocalLifecycleOwner.current.lifecycle,
    minActiveState: Lifecycle.State = Lifecycle.State.STARTED
): Flow<T> = remember(flow, lifecycle) {
    flow.flowWithLifecycle(
        lifecycle = lifecycle,
        minActiveState = minActiveState
    )
}

[Lucien Guimaraes]

flowWithLifecycle is an API from which library ?

[brandonmcansh]

androidx.lifecycle

[brandonmcansh]

2.4.0-alpha01

[Lucien Guimaraes]

ah I'm using the stable version that's why (2.3.1)

[Lucien Guimaraes]

and this solved the cast issue ?

[brandonmcansh]

started w/ this implementation so I didnt actually hit a cast issue. But this is running right now in production w/ no issues.

[Chuck Jazdzewski [G]]

@Lucien Guimaraes Do you have a small reproducible case I can look at? I cannot tell what might be wrong from the snippet provided.

[Lucien Guimaraes]

I don't have a small project to reproduce the issue, as for now I was implementing it in a prod app. But I can share the error log

[Lucien Guimaraes]

error_log.txt

[Lucien Guimaraes]

btw I tried your option @brandonmcansh and I still have the crash

[brandonmcansh]

oh your UIState is a sealed class?

[Lucien Guimaraes]

yes, that's what I said in the first message 😅 and you can see that in the snippet

[brandonmcansh]

those objects don’t equal

[brandonmcansh]

so they can’t cast across

[brandonmcansh]

i’d convert your viewstate to a data class and handle actions

[brandonmcansh]

hoist the navigation effect and handle it higher than your viewstate

[Lucien Guimaraes]

those objects don’t equal

so they can’t cast across

What do you mean by that ? 🤔 I'm not sure to understand

[miqbaldc]

did it means, we have to use data class instead of using sealed class when collecting the state? cmiiw

[brandonmcansh]

The sealed class entities are only comparable via is and aren't actually equal entities

[Lucien Guimaraes]

Just fixed my crash, it was an hoist issue and it's now working like a charm

[Lucien Guimaraes]

The sealed class entities are only comparable via is and aren't actually equal entities

Yeah I know that but I don't know why you said it was an issue regarding my case, I'm already doing a comparison with is

[miqbaldc]

Did you mean hoist issue, you used flowWithLifecycle to fix ur crash?