Is there a better way to keep parallelism in the `initialize kotlinlang #coroutines

import kotlinx.coroutines.*

fun main() = runBlocking {
    println(initializeStuffAndGetFoo())
}

suspend fun initializeStuffAndGetFoo() = withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
    listOf(
        async { getFooValue() },
        async { initA() },
        async { initB() },
    ).awaitAll().first() as String
}

suspend fun getFooValue(): String {
    delay(2_000)
    return "Foo"
}

suspend fun initA() = delay(1_000)
suspend fun initB() = delay(3_000)

I forgot that

async

starts eagerly by default so we can use something like that, can't we ?

import kotlinx.coroutines.*

fun main() = runBlocking {
    println(initializeStuffAndGetFoo())
}

suspend fun initializeStuffAndGetFoo() = withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
    val fooAsync = async { getFooValue() }
    listOf(
        async { initA() },
        async { initB() },
    ).awaitAll()

    fooAsync.await()
}

suspend fun getFooValue(): String {
    delay(2_000)
    return "Foo"
}

suspend fun initA() = delay(1_000)
suspend fun initB() = delay(3_000)

Joffrey

08/11/2022, 2:03 PM

You also don't even need to launch the other 2 using

async

, you could use

lauch

for the other 2 and not even await them (

withContext

would do it)

Nino

08/11/2022, 2:05 PM

Wouldn't

initA()

and

initB()

become sequential this way ?

Nevermind, I need to use 2 launches obviously. The heat is killing my brain lol Final code ? :

import kotlinx.coroutines.*

fun main() = runBlocking {
    println(initializeStuffAndGetFoo())
}

suspend fun initializeStuffAndGetFoo() = coroutineScope {
    launch { initA() }
    launch { initB() }
    getFooValue()
}

suspend fun getFooValue(): String {
    println("Waiting for foo value...")
    delay(2_000)
    println("Waiting for foo value done!")
    return "Foo"
}

suspend fun initA() {
    println("Waiting for A...")
    delay(1_000)
    println("Waiting for A done!")
} 
suspend fun initB() {
    println("Waiting for B...")
    delay(3_000)
    println("Waiting for B done!")
}

Joffrey

08/11/2022, 2:57 PM

Exactly

Nino

08/11/2022, 2:58 PM

Thanks a lot ! 🙂

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