If I have a channel, how can I “channel.take(5)“, ie. get a list containing the 5 items I would get if I channel.receive() 5 times?

Does not work: https://pl.kotl.in/imipXeoIe from what I can see,

channel.take

is marked with ObsoleteCoroutineAPI

1. You've forgot to close the channel when you're done with it. 2. You've created rendezvous channel without buffer, so as soon as you

send

to it, coroutine suspends till someone `receive`s a value, and in your case there is only one coroutine so noone would be able to consume values. So to make the code work, 1. Add

channel.close()

to the end, 2. Add

Unit

as the last statement (or don't use single-expression for your

main

with

runBlocking

) 3. Either create buffered channel (

Channel<Int>(10)

) or split the sending and receiving parts into concurrent coroutines, for example, by wrapping

repeat

in

launch { ... }

.

As well, ObsoleteCoroutineAPI doesn't make it any less valid until they provide the alternatives

@r4zzz4k Conflated channels NEVER suspend on

send

@Dico yeah, that had to be rendezvous, not conflated -- my bad, thanks for pointing out!

Thanks for the discussion guys!

Definitely a typo there. Channels are Rendezvous by default :)

Guys! I managed to do it very nicely, just tiny modification from my original example. https://pl.kotl.in/sJFQEt0GO I had just forgotten to send to the channel from within a coroutine. Not totally clear to me why it makes such a difference though 🤔

Because concurrency is explicit in Kotlin coroutines. Without it, your

send

method suspends your method until something `receive`s it. Since you were doing

send

and

receive

in the same coroutine, the

send

was suspending your coroutine, which means it hung forever because no one else was going to receive.

This makes it totally clear! Thank you @bdawg.io!!