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/*
* Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
*/
// This file was automatically generated from select-expression.md by Knit tool. Do not edit.
package kotlinx.coroutines.guide.exampleSelect05
import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*
import kotlinx.coroutines.selects.*
fun CoroutineScope.switchMapDeferreds(input: ReceiveChannel<Deferred<String>>) = produce<String> {
var current = input.receive() // start with first received deferred value
while (isActive) { // loop while not cancelled/closed
val next = select<Deferred<String>?> { // return next deferred value from this select or null
input.onReceiveCatching { update ->
update.getOrNull()
}
current.onAwait { value ->
send(value) // send value that current deferred has produced
input.receiveCatching().getOrNull() // and use the next deferred from the input channel
}
}
if (next == null) {
println("Channel was closed")
break // out of loop
} else {
current = next
}
}
}
fun CoroutineScope.asyncString(str: String, time: Long) = async {
delay(time)
str
}
fun main() = runBlocking<Unit> {
val chan = Channel<Deferred<String>>() // the channel for test
launch { // launch printing coroutine
for (s in switchMapDeferreds(chan))
println(s) // print each received string
}
chan.send(asyncString("BEGIN", 100))
delay(200) // enough time for "BEGIN" to be produced
chan.send(asyncString("Slow", 500))
delay(100) // not enough time to produce slow
chan.send(asyncString("Replace", 100))
delay(500) // give it time before the last one
chan.send(asyncString("END", 500))
delay(1000) // give it time to process
chan.close() // close the channel ...
delay(500) // and wait some time to let it finish
}
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