I was also wondering if it is possible to run `Coroutines` with compose?

# compose

[Archie]

I was also wondering if it is possible to run Coroutines with compose?

[Adam Powell]

launchInComposition will launch a coroutine into a scope managed by the composition. If the call leaves the composition the scope is cancelled for you. https://developer.android.com/reference/kotlin/androidx/compose/package-summary#launchincomposition

[Archie]

Wow thank you very much. I've been searching for quite a while but I didnt see this. Thanks!

[Archie]

So ive tried out launchInComposition , now I was wondering how I could run my coroutines without it getting cancelled by device rotation similar to launching coroutines in viewModelScope. Is this possible?

[Adam Powell]

Yes, you can still launch into a viewModelScope in the usual way

[Archie]

That means I have to create a ViewModel luanch the coroutine inside that ViewModel with viewModelScope? correct?

[Adam Powell]

For the moment anyway. I think we had a couple of compose extensions that behave similarly to the by viewModels() API for fragments/activities floating around but I'm not sure which things made it into the actual api just yet 🙂

[Timo Drick]

You could also just create a singleton (object) and launch your coroutine there. When you do not want to cancel it when the view gets disposed. But than you can not change the UI as an result of the execution. So it depends on what you want to do.

[Adam Powell]

This is where a pattern of launchInComposition making suspending calls to a ViewModel makes a lot of sense

[Adam Powell]

the suspend function on the viewmodel can do things like viewModelScope.async { ... } internally, store the Deferred, and return the .await() of that operation

[Adam Powell]

then future calls can await the one that's already in progress

[Adam Powell]

UI updates stay scoped to the UI, and the operation itself stays scoped elsewhere and can multiplex for multiple awaiters

[Timo Drick]

In my opinion in practice often the viewmodel lifecycle is not appropriate for most operations that are not directly tied to a fragment or an activity. But yes of course now with compose we only need one activity. But than the viewmodel is at the end the same like an object?

[Adam Powell]

Substitute your backing repository scope then; the key part is that you let the operation and awaiting its result happen in different scopes 🙂

[Adam Powell]

tbh I find very little use for viewModelScope in my own code thanks to this 🤷‍♂️

[Archie]

tbh I find very little use for viewModelScope in my own code thanks to this

I got confused with this. So do we need viewModel or not? 🤔

[Adam Powell]

ViewModel itself as a transport for transformed data caches across configuration changes, sure, but the viewModelScope CoroutineScope I don't tend to use very often. It depends on what you want to scope and why

[Archie]

For the moment anyway. I think we had a couple of compose extensions that behave similarly to the by viewModels() API for fragments/activities floating around but I'm not sure which things made it into the actual api just yet 🙂

I accidentally found this in compose:

val mainViewModel: MainViewModel = viewModel()

where viewModel() is a @Composable function.

(Thank for pointing out the existing api <3)

Is it right to assume that the ViewModel created here is scope to the Activity /`Fragment` Hosting the @Composable function?