Is it possible to listen to a `ReceiveChannel` to ...

# coroutines

[streetsofboston]

Is it possible to listen to a ReceiveChannel to get notified when it is closed, either through an error or without one (just normally closed)?

[Allan Wang]

See https://github.com/Kotlin/kotlinx.coroutines/issues/341

[streetsofboston]

Thanks! This issue is closed… will the Channel.invokeOnClose make it into the library or not…? 🙂

[Allan Wang]

SendChannel.invokeOnClose exists. Isn't that what you want? If you want to wait for all received events you might be able to consume all events (doing nothing) and handle stuff afterwards

[Allan Wang]

Or you could try adding a deferred call in invoke on close

[streetsofboston]

It want a ReceiveChannel.invokeOnClose, if possible.

[streetsofboston]

I used a work around by creating a brand new channel, the target, and sending events from the source channel using a for-loop. Surrounding this in a try will get me a close-with-error. A regular close will be signaled by the for-loop terminating.

Still, it’s extra code (creating new channel, for-loop, sending to new channel) for just wanting to listen to a close.

[louiscad]

@streetsofboston The function is there, the commit adding it closed this issue I reported. I now happily use it in my projects.

[streetsofboston]

@louiscad Is ReceiveChannel.invokeOnClose there? I can’t find it…. it’s only available on SendChannel

[louiscad]

@streetsofboston Which kotlinx.coroutines version and which target (JVM? JS?)? You can see the declaration in the commit closing the issue also.

[streetsofboston]

@louiscad
Coroutines lib version 1.0.1 on JVM

[louiscad]

@streetsofboston My bad, it's on SendChannel (which makes more sense though). I can definitely see and use it in 1.1.1

[streetsofboston]

It makes a lot of sense on both types of channels, maybe even more so than on SendChannel. The ReceiveChannel would want both to receive values and to receive closing-events (with or without error) 🙂

[louiscad]

In that case, open an issue on GitHub, explain your use case there and link it back here.

[streetsofboston]

Will do! Thanks!