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Exposing unique subscription handling for custom flow operations (#560)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| package com.airbnb.mvrx | ||
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| import androidx.lifecycle.DefaultLifecycleObserver | ||
| import androidx.lifecycle.LifecycleOwner | ||
| import androidx.lifecycle.lifecycleScope | ||
| import kotlinx.coroutines.CoroutineStart | ||
| import kotlinx.coroutines.Job | ||
| import kotlinx.coroutines.flow.Flow | ||
| import kotlinx.coroutines.flow.collectLatest | ||
| import kotlinx.coroutines.flow.distinctUntilChanged | ||
| import kotlinx.coroutines.flow.dropWhile | ||
| import kotlinx.coroutines.flow.onCompletion | ||
| import kotlinx.coroutines.flow.onEach | ||
| import kotlinx.coroutines.launch | ||
| import kotlinx.coroutines.plus | ||
| import kotlinx.coroutines.yield | ||
| import java.util.concurrent.ConcurrentHashMap | ||
|
|
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| internal fun <T : Any?> Flow<T>.collectLatest( | ||
| lifecycleOwner: LifecycleOwner, | ||
| lastDeliveredStates: ConcurrentHashMap<String, Any?>, | ||
| activeSubscriptions: MutableSet<String>, | ||
| deliveryMode: DeliveryMode, | ||
| action: suspend (T) -> Unit | ||
| ): Job { | ||
| val flow = when { | ||
| MavericksTestOverrides.FORCE_DISABLE_LIFECYCLE_AWARE_OBSERVER -> this | ||
| deliveryMode is UniqueOnly -> { | ||
| this.assertOneActiveSubscription(lifecycleOwner, activeSubscriptions, deliveryMode.subscriptionId) | ||
| .dropWhile { lastDeliveredStates.containsKey(deliveryMode.subscriptionId) && it == lastDeliveredStates[deliveryMode.subscriptionId] } | ||
| .flowWhenStarted(lifecycleOwner) | ||
| .distinctUntilChanged() | ||
| .onEach { lastDeliveredStates[deliveryMode.subscriptionId] = it } | ||
| } | ||
| else -> flowWhenStarted(lifecycleOwner) | ||
| } | ||
|
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| val scope = lifecycleOwner.lifecycleScope + Mavericks.viewModelConfigFactory.subscriptionCoroutineContextOverride | ||
| return scope.launch(start = CoroutineStart.UNDISPATCHED) { | ||
| // Use yield to ensure flow collect coroutine is dispatched rather than invoked immediately. | ||
| // This is necessary when Dispatchers.Main.immediate is used in scope. | ||
| // Coroutine is launched with start = CoroutineStart.UNDISPATCHED to perform dispatch only once. | ||
| yield() | ||
| flow.collectLatest(action) | ||
| } | ||
| } | ||
|
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| @Suppress("EXPERIMENTAL_API_USAGE") | ||
| internal fun <T : Any?> Flow<T>.assertOneActiveSubscription(lifecycleOwner: LifecycleOwner, activeSubscriptions: MutableSet<String>, subscriptionId: String): Flow<T> { | ||
| val observer = object : DefaultLifecycleObserver { | ||
| override fun onCreate(owner: LifecycleOwner) { | ||
| if (activeSubscriptions.contains(subscriptionId)) error(duplicateSubscriptionMessage(subscriptionId)) | ||
| activeSubscriptions += subscriptionId | ||
| } | ||
|
|
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| override fun onDestroy(owner: LifecycleOwner) { | ||
| activeSubscriptions.remove(subscriptionId) | ||
| } | ||
| } | ||
|
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| lifecycleOwner.lifecycle.addObserver(observer) | ||
| return onCompletion { | ||
| activeSubscriptions.remove(subscriptionId) | ||
| lifecycleOwner.lifecycle.removeObserver(observer) | ||
| } | ||
| } | ||
|
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| private fun duplicateSubscriptionMessage(subscriptionId: String) = """ | ||
| Subscribing with a duplicate subscription id: $subscriptionId. | ||
| If you have multiple uniqueOnly subscriptions in a MvRx view that listen to the same properties | ||
| you must use a custom subscription id. If you are using a custom MvRxView, make sure you are using the proper | ||
| lifecycle owner. See BaseMvRxFragment for an example. | ||
| """.trimIndent() |
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17 changes: 0 additions & 17 deletions
17
mvrx/src/main/kotlin/com/airbnb/mvrx/MavericksViewIdViewModel.kt
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20 changes: 20 additions & 0 deletions
20
mvrx/src/main/kotlin/com/airbnb/mvrx/MavericksViewInternalViewModel.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,20 @@ | ||
| package com.airbnb.mvrx | ||
|
|
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| import androidx.lifecycle.SavedStateHandle | ||
| import androidx.lifecycle.ViewModel | ||
| import java.util.UUID | ||
| import java.util.concurrent.ConcurrentHashMap | ||
|
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| class MavericksViewInternalViewModel(state: SavedStateHandle) : ViewModel() { | ||
| internal val lastDeliveredStates: ConcurrentHashMap<String, Any?> = ConcurrentHashMap<String, Any?>() | ||
| internal val activeSubscriptions: MutableSet<String> = mutableSetOf() | ||
| internal val mavericksViewId = state[PERSISTED_VIEW_ID_KEY] ?: generateUniqueId().also { id -> | ||
| state[PERSISTED_VIEW_ID_KEY] = id | ||
| } | ||
|
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| private fun generateUniqueId() = "MavericksView_" + UUID.randomUUID().toString() | ||
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| companion object { | ||
| private const val PERSISTED_VIEW_ID_KEY = "mavericks:persisted_view_id" | ||
| } | ||
| } |
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