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/*
* Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
*/
package kotlinx.coroutines.rx3
import io.reactivex.rxjava3.core.*
import kotlinx.coroutines.*
import kotlin.coroutines.*
/**
* Creates cold [maybe][Maybe] that will run a given [block] in a coroutine and emits its result.
* If [block] result is `null`, [onComplete][MaybeObserver.onComplete] is invoked without a value.
* Every time the returned observable is subscribed, it starts a new coroutine.
* Unsubscribing cancels running coroutine.
* Coroutine context can be specified with [context] argument.
* If the context does not have any dispatcher nor any other [ContinuationInterceptor], then [Dispatchers.Default] is used.
* Method throws [IllegalArgumentException] if provided [context] contains a [Job] instance.
*/
public fun <T> rxMaybe(
context: CoroutineContext = EmptyCoroutineContext,
block: suspend CoroutineScope.() -> T?
): Maybe<T> {
require(context[Job] === null) { "Maybe context cannot contain job in it." +
"Its lifecycle should be managed via Disposable handle. Had $context" }
return rxMaybeInternal(GlobalScope, context, block)
}
private fun <T> rxMaybeInternal(
scope: CoroutineScope, // support for legacy rxMaybe in scope
context: CoroutineContext,
block: suspend CoroutineScope.() -> T?
): Maybe<T> = Maybe.create { subscriber ->
val newContext = scope.newCoroutineContext(context)
val coroutine = RxMaybeCoroutine(newContext, subscriber)
subscriber.setCancellable(RxCancellable(coroutine))
coroutine.start(CoroutineStart.DEFAULT, coroutine, block)
}
private class RxMaybeCoroutine<T>(
parentContext: CoroutineContext,
private val subscriber: MaybeEmitter<T>
) : AbstractCoroutine<T>(parentContext, true) {
override fun onCompleted(value: T) {
try {
if (value == null) subscriber.onComplete() else subscriber.onSuccess(value)
} catch (e: Throwable) {
handleUndeliverableException(e, context)
}
}
override fun onCancelled(cause: Throwable, handled: Boolean) {
try {
if (!subscriber.tryOnError(cause)) {
handleUndeliverableException(cause, context)
}
} catch (e: Throwable) {
handleUndeliverableException(e, context)
}
}
}
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