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72
...libs/fx/arrow-fx-coroutines/src/commonMain/kotlin/arrow/fx/coroutines/await/AwaitScope.kt
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| @@ -0,0 +1,72 @@ | ||
| package arrow.fx.coroutines.await | ||
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| import arrow.atomic.Atomic | ||
| import arrow.atomic.update | ||
| import kotlinx.coroutines.async as coroutinesAsync | ||
| import kotlinx.coroutines.CoroutineScope | ||
| import kotlinx.coroutines.CoroutineStart | ||
| import kotlinx.coroutines.Deferred | ||
| import kotlinx.coroutines.awaitAll | ||
| import kotlinx.coroutines.coroutineScope | ||
| import kotlin.coroutines.CoroutineContext | ||
| import kotlin.coroutines.EmptyCoroutineContext | ||
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| public suspend fun <A> await( | ||
| block: suspend AwaitScope.() -> A | ||
| ): A = coroutineScope { block(AwaitScope(this)) } | ||
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| public suspend fun <A> CoroutineScope.await( | ||
| block: suspend AwaitScope.() -> A | ||
| ): A = block(AwaitScope(this)) | ||
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| /** | ||
| * Within an [AwaitScope], any call to [kotlinx.coroutines.Deferred.await] | ||
| * causes all the other [Deferred] in the same block to be awaited too. | ||
| * That way you can get more concurrency without having to sacrifice | ||
| * readability. | ||
| * | ||
| * ```kotlin | ||
| * suspend fun loadUserInfo(id: UserId): UserInfo = await { | ||
| * val name = async { loadUserFromDb(id) } | ||
| * val avatar = async { loadAvatar(id) } | ||
| * UserInfo( | ||
| * name.await(), // <- at this point every 'async' is 'await'ed | ||
| * avatar.await() // <- so when you reach this 'await', the value is already there | ||
| * ) | ||
| * } | ||
| * | ||
| * suspend fun loadUserInfoWithoutAwait(id: UserId): UserInfo { | ||
| * val name = async { loadUserFromDb(id) } | ||
| * val avatar = async { loadAvatar(id) } | ||
| * awaitAll(name, avatar) // <- this is required otherwise | ||
| * return UserInfo( | ||
| * name.await(), | ||
| * avatar.await() | ||
| * ) | ||
| * } | ||
| * ``` | ||
| */ | ||
| public class AwaitScope( | ||
| private val scope: CoroutineScope | ||
| ): CoroutineScope by scope { | ||
| private val tasks: Atomic<List<Deferred<*>>> = Atomic(emptyList()) | ||
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| public fun <T> async( | ||
| context: CoroutineContext = EmptyCoroutineContext, | ||
| start: CoroutineStart = CoroutineStart.DEFAULT, | ||
| block: suspend CoroutineScope.() -> T | ||
| ): Deferred<T> { | ||
| val deferred = coroutinesAsync(context, start, block) | ||
| tasks.update { it + deferred } | ||
| return Await(deferred) | ||
| } | ||
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| private inner class Await<T>( | ||
| private val deferred: Deferred<T> | ||
| ): Deferred<T> by deferred { | ||
| override suspend fun await(): T { | ||
| tasks.getAndSet(emptyList()).awaitAll() | ||
| return deferred.await() | ||
| } | ||
| } | ||
| } |