I have a parent `CoroutineScope` which has a long lifecycle kotlinlang #coroutines

which has a long lifecycle. I want to make another scope which has a shorter lifecycle (potentially several in the same span as the 'parent'). If the parent scope is cancelled I want both parent and the shorter lifecycle scope to be cancelled as far as i can tell you can't inherit scopes like this. another (seemingly bad) idea I have is to maintain a collection of `Job`s for the shorter lifecycle group, which will allow me to cancel everything in that collection, or if the parent scope is cancelled, they would all be launched under it anyway, and get cancelled

Joffrey

04/19/2022, 8:38 PM

as far as I can tell you can't inherit scopes like this

You can create such a child scope by creating it with an explicit job that has the job from the parent scope as parent:

CoroutineScope(Job(parent = parentScope.job))

(I think there is a

.job

extension property like this on the coroutine scope)

Otherwise if you use regular coroutine builders in the parent scope you automatically get a child scope inside them:

parentScope.launch { // this = child scope
   ...
}

Zach Klippenstein (he/him) [MOD]

04/19/2022, 9:19 PM

Yea, you can definitely do this, this is the core idea behind structured concurrency

William Reed

04/19/2022, 9:41 PM

Thanks @Joffrey i'll give that a try

haven't tested it yet but I could access the job through

parentScope.coroutineContext.job

thanks again joffrey. seems to be working great after testing. of course the

launch

example is obvious with normal structured concurrency. didn't realize i could do this to jobs though

Joffrey

04/19/2022, 9:56 PM

You're welcome ☺️ Yeah the job gymnastics is not advertised that much. The important thing to keep in mind is that the part that is responsible for structured concurrency is in fact the job, not the scope per se

☝️🏻 1

William Reed

04/19/2022, 9:59 PM

yeah makes sense. i didn't realize the scope maintained a job like that. perhaps i should read a bit more on that

2 Views

#coroutines Join Slack