example-select-01.kt

/*
 * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
 */

// This file was automatically generated from coroutines-guide.md by Knit tool. Do not edit.
package kotlinx.coroutines.guide.select01

import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*
import kotlinx.coroutines.selects.*

fun CoroutineScope.fizz() = produce<String> {
    while (true) { // sends "Fizz" every 300 ms
        delay(300)
        send("Fizz")
    }
}

fun CoroutineScope.buzz() = produce<String> {
    while (true) { // sends "Buzz!" every 500 ms
        delay(500)
        send("Buzz!")
    }
}

suspend fun selectFizzBuzz(fizz: ReceiveChannel<String>, buzz: ReceiveChannel<String>) {
    select<Unit> { // <Unit> means that this select expression does not produce any result 
        fizz.onReceive { value ->  // this is the first select clause
            println("fizz -> '$value'")
        }
        buzz.onReceive { value ->  // this is the second select clause
            println("buzz -> '$value'")
        }
    }
}

fun main() = runBlocking<Unit> {
    val fizz = fizz()
    val buzz = buzz()
    repeat(7) {
        selectFizzBuzz(fizz, buzz)
    }
    coroutineContext.cancelChildren() // cancel fizz & buzz coroutines
}