```fun ProgressThingy(duration: Long, running: Flo...

# coroutines

[ursus]

fun ProgressThingy(duration: Long, running: Flow<Boolean>): Flow<Float> {
    return callbackFlow {
        val animator = ValueAnimator.ofFloat(0F, 1F)
        animator.duration = duration
        animator.addUpdateListener {
            trySend(it.animatedFraction)
        }
        animator.addListener(onCancel = {
            cancel()
        })
        animator.start()

        running.collect {
            if (it) animator.resume() else animator.pause()
        }

        awaitClose {
            animator.cancel()
        }
    }
}

does anyone see a problem with collecting the running signal like that within the callback flow scope? it appears to work fine

[ursus]

ok turns out the collect obviosuly suspends so awaitClose is never registered since running never completes

Any idea I could do this pattern? Rx used it

[Joffrey]

You could launch the collection in a coroutine so you can reach awaitClose

[ursus]

doh.. thank you!

[ursus]

If I could ask, now it suspend on the awaitClose until the flow is canceled. How could I make it complete when the animator completes?

[ursus]

Im aware that it completes once the lambda returns, sooo idk

[Joffrey]

You can make the callback flow complete by calling close() on the channel it gives you, but I don't know the animator API so not sure how to know it is complete

[ursus]

oh, interesting that its not wrapped

[Joffrey]

What do you mean?

[ursus]

that I have to talk to the channel directly, not via some indirection as with trySend

[ursus]

hm there is a close in there as well

[Joffrey]

trySend is provided by the producer scope I believe, and close should be also provided the same way

[ursus]

yea so why leak the channel reference like that

[Joffrey]

I don't believe it's meant to be hidden. Rather, the producer scope provides convenient "shortcuts", but the basics are there if you need them (like pass the channel around etc)

[ursus]

alright so the close is same as calling channel.close ?

[Joffrey]

I believe so yes, but I can't check because I'm afk. You should be able to check that in the IDE by navigating to the declaration. I would bet it calls channel.close()

[ursus]

well it doesnt but it does behave as expected

[ursus]

public override fun close(cause: Throwable?): Boolean {
        val closed = Closed<E>(cause)
        /*
         * Try to commit close by adding a close token to the end of the queue.
         * Successful -> we're now responsible for closing receivers
         * Not successful -> help closing pending receivers to maintain invariant
         * "if (!close()) next send will throw"
         */
        val closeAdded = queue.addLastIfPrev(closed) { it !is Closed<*> }
        val actuallyClosed = if (closeAdded) closed else queue.prevNode as Closed<*>
        helpClose(actuallyClosed)
        if (closeAdded) invokeOnCloseHandler(cause)
        return closeAdded // true if we have closed
    }