I dont understand this. The warning says suspending fun has a CoroutineScope receiver, but the secon...

# coroutines

[Lucas]

I dont understand this.
The warning says suspending fun has a CoroutineScope receiver, but the second class fails to find the "launch" method.
Is this a bug or am i really misunderstanding this?

[Trevor Stone]

Not sure exactly what you're trying to do, but

class Test{
 suspend fun test() = coroutineScope{
 launch{ do things}
}
}

might be what you're looking for

[Trevor Stone]

but that launch will stop returning from test() until it completes

[Lucas]

Well, i'm trying to use coroutines with JavaFX, but that doesnt seem to be very usual and i didnt find much on it apart from the Dispatchers.JavaFX (or Main)
One elegant solution i found was to make my components extend the CoroutineScope and clear it accordingly to javafx components lifecycle

The classes were minimal reproducers
But regardless of what i'm trying to do, i still dont quite understand the warning. Why cant i call launch from a suspending function?

[Lucas]

Ok i tried your code and i makes a bit more sense now. Still some things i need to figure out tho, thanks!

[Ivan Pavlov]

Your outer class "test" implements coroutinescope, so launch in your function is this.launch

[Chrimaeon]

You are already in a suspend function. There is no need to launch a coroutine. That's what the warning is telling you.

[Lucas]

I dont think thats it @Chrimaeon

suspend fun test() {
 launch{ do things}
 do other things
}

What if i wanted this? It would still show a warning

[Ivan Pavlov]

To get access to coroutine scope in suspending function you can do

suspend fun test() {
  coroutineScope {
    // access scope here
  }
}

[Chrimaeon]

Sure, but then also you’ll need to wrap the launch in a “new” coroutineScope{} like already mentioned, to give the job it’s own inner scope

[Lucas]

Yeah i think i was misunderstanding some basic concepts about context vs scope

[Lucas]

Like why could i use withContext but not launch

[Trevor Stone]

withContext provides a coroutineScope in the block and doesn't require one to run

[louiscad]

Implementing CoroutineScope is the problem. Should have a private property instead, and use coroutineScope { } inside suspend functions.