is there a coroutines implementation for general JVM apps, e.g. a desktop application?

# coroutines

[Rainer Schlonvoigt]

is there a coroutines implementation for general JVM apps, e.g. a desktop application?

[Dominaezzz]

Yes but for specific GUI frameworks. JavaFX, Swing, etc.

[Rainer Schlonvoigt]

ouch

[Rainer Schlonvoigt]

i am using coroutines for server things... did not expect UI to be involved

[Dominaezzz]

Then why are you using Dispatchers.Main?

[Dominaezzz]

You should be using Dispatchers.Default, <http://Dispatchers.IO|Dispatchers.IO> and custom dispatchers if you see fit.

[Rainer Schlonvoigt]

That solved it, thank you! 😄

[louiscad]

If your app starting point is the main function, you can just start it that way:

suspend fun main(): Unit = coroutineScope {
    // app starts here, launch coroutines and all
}

[Dominaezzz]

Might as well just use runBlocking, right?

[louiscad]

suspend fun main uses Dispatchers.Default in its coroutineContext, which is multi-threaded (at least 2 threads, configured for number of CPU cores), while runBlocking reuses the JVM single initial thread.

[Dominaezzz]

Reuse appeals to me. Also this can be done.

fun main() = runBlocking(Dispatchers.Default) {
    // stuff
}

[Dominaezzz]

Although, that doesn't look much better that your initial example. So 🤷🏼 I guess.

[louiscad]

@elizarov Does suspend fun main inject/reuse the JVM initial thread into Dispatchers.Default? If not, is it possible without major drawbacks?

[elizarov]

The major drawback is that UI apps might also have suspend fun main

[Dico]

@louiscad suspend fun main can't use Dispatchers.Default because that's kotlinx

[Dico]

Although it will default to that dispatcher in kotlinx because context contains no dispatcher

[louiscad]

It'd be nice to have it configurable then.

[louiscad]

@Dico I remember reading it checking if kotlinx.coroutines is in the classpath.

[Dico]

I take that back, I'm pretty sure it's single thread event loop

[Dico]

That would be pretty poor design honestly

[louiscad]

I know suspend fun main does result in a multi-threaded coroutineContext regardless.