Why prefer suspending functions instead of CoroutineScope extensions? An example with vegetables.

Why prefer suspending functions instead of CoroutineScope extensions? An example with vegetables.

One of the people behind Kotlin wrote this article called Explicit concurrency, in it, when comparing suspending functions vs

CoroutineScope

extensions he says:

As a rule of thumb, you should prefer suspending functions, since concurrency is not a safe default to have. Anyone with a suspending function at hand can explicitly use launch { … } to initiate its concurrent execution.

I don’t understand what is meant by this:

Anyone with a suspending function at hand can explicitly use launch { … } to initiate its concurrent execution.

This is an example of an extension function he uses in the articles:


fun CoroutineScope.launchFooBar() = launch { foo(bar()) }

So the example is wrong? Are we not supposed to call launch from extension functions? I’m confused as to how should I “properly” use

CoroutineScope

extensions.

How I understand it

Maybe

CoroutineScope

extensions are supposed to “abstract away” the launching of coroutines. Maybe they should even be private functions. Then I can call them with structured concurrency with a regular suspending function.

I tried to come up with an example where you grow vegetables:


enum class Vegetable { TURNIP, ONION, POTATO } private fun CoroutineScope.growVegetableInBackground(vegetable: Vegetable) = launch { // grow the vegetable with different ways depending on what type it is println("Growing $vegetable") delay(1000) println("$vegetable done!") } suspend fun growAll(vegetables: List<Vegetable>) = coroutineScope { println("Growing all vegetables!") vegetables.forEach { growVegetableInBackground(it) } } fun main() = runBlocking { val vegetables = listOf(Vegetable.ONION, Vegetable.POTATO, Vegetable.TURNIP) growAll(vegetables) }

This is what is printed to the console:


Growing all vegetables! Growing ONION Growing POTATO Growing TURNIP ONION done! POTATO done! TURNIP done!

Is this the way?

submitted by /u/cris_null
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