Is it possible to set multiple CompletionHandler o...

# coroutines

[Sam]

Is it possible to set multiple CompletionHandler on a job?

[zak.taccardi]

IIRC correctly, use.

for these kinds of questions, it’s useful to write a quick unit test to confirm

[zak.taccardi]

just register multiple completion handlers that output some logs on a scope, and run it

[Sam]

Oh yeah, i did try, i don't see API support

[Sam]

public fun invokeOnCompletion(handler: CompletionHandler): DisposableHandle

[Sam]

seems like the next request overwrites the previous one

[bdawg.io]

@Sam “seems” as in you’re registering two handlers in code and the first one isn’t getting called when you execute the code?

[Sam]

yeah

[Sam]

in my case, i'm using a helper method from a library

[Sam]

library is setting a CompletionHandler for its own cleanup

[Sam]

so i'm wondering how i can set one? I guess, i will have to ask the API to provide another callback

[Sam]

kind of chained implementation

[bdawg.io]

I’m not sure what your test code is, but I wrote one real quick:

suspend fun main() = coroutineScope<Unit> {
    val job = launch { delay(1000) }

    job.invokeOnCompletion { println("handler one called") }
    job.invokeOnCompletion { println("handler two called") }
    job.invokeOnCompletion { println("handler three called") }
}

prints out

handler one called
handler two called
handler three called

[Sam]

Thanks, this does work

[Sam]

I'm not sure why my callback fails

[bdawg.io]

If your callback throws an exception:

Installed [handler] should not throw any exceptions. If it does, they will get caught, wrapped into [CompletionHandlerException], and rethrown, potentially causing crash of unrelated code.

[Sam]

Hmmm, okay, will check the library implementation

[Sam]

Thanks for the tip