Flow's onCompletion not being called

Hi,

As the guideline in https://codelabs.developers.google.com/codelabs/advanced-kotlin-coroutines/index.html?index=..%2F..index#13 suggests, the codelab is finished:

growZoneChannel.asFlow()
            .mapLatest { growZone ->
                _spinner.value = true
                if (growZone == NoGrowZone) {
                    plantRepository.tryUpdateRecentPlantsCache()
                } else {
                    plantRepository.tryUpdateRecentPlantsForGrowZoneCache(growZone)
                }
            }
            .onCompletion {
                _spinner.value = false
            }
            .catch { throwable ->
                _snackbar.value = throwable.message
            }
            .launchIn(viewModelScope) 

Even if you do the latest challenge to refactor all this, we would end up in this case:

init {
        // When creating a new ViewModel, clear the grow zone and perform any related udpates
        clearGrowZoneNumber()

        loadDataFor(growZoneChannel) { growZone ->
            _spinner.value = true
            if (growZone == NoGrowZone) {
                plantRepository.tryUpdateRecentPlantsCache()
            } else {
                plantRepository.tryUpdateRecentPlantsForGrowZoneCache(growZone)
            }
        }
    }

//where the loadDataFor is just:

private fun <T> loadDataFor(source: ConflatedBroadcastChannel<T>, block: suspend (T) -> Unit) {
        source.asFlow()
            .mapLatest {
                block(it)
            }
            .onCompletion {
                _spinner.value = false
            }
            .catch { throwable ->
                _snackbar.value = throwable.message
            }
            .launchIn(viewModelScope)
    }

However, the onCompletion method is not being called, and causing the _spinner value not to be updated at the end. I don’t know what’s wrong but I did try my solution and did try finished_code directory also.

[khpproud]

I tried like this:

fun <T> loadDataFor(source: ConflatedBroadcastChannel<T>, block: suspend (T) -> Unit) {
        source.asFlow()
            .mapLatest {
                _spinner.value = true
                block(it)
            }
            .onEach { _spinner.value = false }
            .onCompletion { _spinner.value = false }
            .catch { _snackbar.value = it.message }
            .launchIn(viewModelScope)
}

The channel is not closed calling explicitly “close()” on viewModel’s lifecycle, so it seems more appropriate to add “onEach”.

[fegan104]

You’re correct. I asked about this issue on Stackoverflow . Looks like the codelab is not correct when it states:

“onCompletion will be called every time the flow above it completes. It’s the same thing as a finally block – it’s a good place to put any code you need to execute during cleanup. Here we’re resetting the spinner.”