DemoCoroutinesChannelResult

Author: Petrus Nguyễn Thái Học

Overview

1. Create MainSingleEvent class.

sealed interface MainSingleEvent<out T : MainSingleEvent<T>> {
 interface Key<out T : MainSingleEvent<T>>
 val key: Key<T>
 data class HomeFragmentResult(val text: String) : MainSingleEvent<HomeFragmentResult> {
 override val key = HomeFragmentResult
 companion object : Key<HomeFragmentResult>
 }
 data class DashboardFragmentResult(val text: String) : MainSingleEvent<DashboardFragmentResult> {
 override val key = DashboardFragmentResult
 companion object : Key<DashboardFragmentResult>
 }
 data class HomeDetailsResult(val text: String) : MainSingleEvent<HomeDetailsResult> {
 override val key = HomeDetailsResult
 companion object : Key<HomeDetailsResult>
 }
 companion object {
 val KEYS: Set<Key<SomeMainSingleEvent>> = setOf(
 HomeFragmentResult,
 DashboardFragmentResult,
 HomeDetailsResult,
 )
 }
}

2. Create MainVM class with buffered channels as event bus.

class MainVM : ViewModel() {
 private val eventChannels: Map<MainSingleEvent.Key<SomeMainSingleEvent>, Channel<SomeMainSingleEvent>> =
 MainSingleEvent.KEYS.associateBy(
 keySelector = { it },
 valueTransform = { Channel<MainSingleEvent<SomeMainSingleEvent>>(Channel.UNLIMITED) }
 )
 fun <T : MainSingleEvent<T>> sendEvent(event: T) {
 checkNotNull(eventChannels[event.key]) { "Must register ${event.key} in MainSingleEvent.Companion.KEYS before using!" }
 .trySend(event)
 .getOrThrow()
 .also { Log.d("@@@", "Sent $event") }
 }
 @Suppress("UNCHECKED_CAST")
 fun <T : MainSingleEvent<T>, K : MainSingleEvent.Key<T>> receiveEventFlow(key: K): Flow<T> =
 checkNotNull(eventChannels[key]) { "Must register $key in MainSingleEvent.Companion.KEYS before using!" }
 .receiveAsFlow()
 .map { it as T }
}

3. Send and receive events in Fragments.

private val mainVM by viewModels<MainVM>(
 ownerProducer = { requireActivity() }
)
// send in HomeFragment
mainVM.sendEvent(MainSingleEvent.HomeFragmentResult("Hello from HomeFragment"))
// receive in others
mainVM.receiveEventFlow(MainSingleEvent.HomeFragmentResult)
 .onEach { Log.d("###", "Received $it") }
 .launchIn(lifecycleScope)