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UDF - Kotlin Flow vs. Rx: OnEachEvent view effects with Flow
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| /** | |
| * Used as a wrapper for data that is exposed via an observable that represents an event. | |
| * Developed by Jose Alcérreca. | |
| * See [https://gist.github.com/JoseAlcerreca/5b661f1800e1e654f07cc54fe87441af#file-event-kt] | |
| */ | |
| open class Event<out T>(private val content: T) { | |
| var hasBeenHandled = false | |
| private set // Allow external read but not write | |
| /** | |
| * Returns the content and prevents its use again. | |
| */ | |
| fun getContentIfNotHandled(): T? { | |
| return if (hasBeenHandled) { | |
| null | |
| } else { | |
| hasBeenHandled = true | |
| content | |
| } | |
| } | |
| /** | |
| * Returns the content, even if it's already been handled. | |
| */ | |
| fun peekContent(): T = content | |
| } |
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| import kotlinx.coroutines.flow.Flow | |
| import kotlinx.coroutines.flow.transform | |
| /** | |
| * Returns a flow which performs the given [action] on each value of the original flow's [Event]. | |
| */ | |
| public fun <T> Flow<Event<T?>>.onEachEvent(action: suspend (T) -> Unit): Flow<T> = transform { value -> | |
| value.getContentIfNotHandled()?.let { | |
| action(it) | |
| return@transform emit(it) | |
| } | |
| } |
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| @ExperimentalCoroutinesApi | |
| data class _FeedViewEffect( | |
| val _isLoading: MutableStateFlow<Event<Boolean?>> = MutableStateFlow(Event(null)) | |
| ) | |
| @ExperimentalCoroutinesApi | |
| data class FeedViewEffect(private val _viewEffect: _FeedViewEffect) { | |
| val isLoading: Flow<Event<Boolean?>> = _viewEffect._isLoading.filterNotNull() | |
| } |
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| viewModel.viewEffect.isLoading.onEachEvent { isLoading -> | |
| if (isLoading == true) | |
| progressBar.visibility = VISIBLE | |
| else { | |
| progressBar.visibility = GONE | |
| swipeToRefresh.isRefreshing = false | |
| } | |
| }.launchIn(lifecycleScope) |
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| private fun initFeed(toRetry: Boolean) { | |
| feedRepository.initFeed(pagedListBoundaryCallback(toRetry)).onEach { results -> | |
| when (results.status) { | |
| LOADING -> _viewEffect._isLoading.value = Event(true) | |
| SUCCESS -> { | |
| _viewEffect._isLoading.value = Event(false) | |
| _viewState._feed.value = results.data | |
| } | |
| ERROR -> { | |
| _viewEffect._isLoading.value = Event(false) | |
| } | |
| } | |
| }.launchIn(viewModelScope) | |
| } |
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