Hello, everyone! Is there a way to apply the `.map...

# coroutines

[Gabriel Melo]

Hello, everyone! Is there a way to apply the .map operator or something similar to a StateFlow and get another StateFlow back?

[Sam]

https://github.com/Kotlin/kotlinx.coroutines/issues/2008

[Sam]

Sounds like the recommendation is to use map { ... }.stateIn(...)

[Gabriel Melo]

Thank you for the answer, but I'm not sure it applies to my use case.
This doesn't mesh well with DataBinding, as I'd need my ViewModel to have access to a CoroutineScope instead of having the collector handle this.

[Gabriel Melo]

My viewmodels are not AAC ones, btw.

[Gabriel Melo]

Also, .stateIn is a suspending function.

[Sam]

There's a non-suspending version if you provide an initial value, which should be easy to do if you're mapping from an existing StateFlow. I can see that it's inconvenient to have to provide a CoroutineScope, but I think it's unavoidable. Since the resulting StateFlow is a shared flow, the work to compute its values always has do be done by the producer, not by the consumer.

[Sam]

Are you able to use the built-in extension scopes? I'm not sure what you meant by "not AAC", I'm not very familiar with android.

[Gabriel Melo]

AAC means Android Architecture Components. I'm not able to use the extensions you mentioned because my view models don't inherit from ViewModel.

[Gabriel Melo]

Interesting that you have to provide a scope when converting from a Flow to a StateFlow but not when creating one from scratch. There's probably something I'm missing.

[Sam]

If you create your own MutableStateFlow then whatever code you write to set values on that flow is acting as the producer. It may not necessarily be a coroutine, but something besides the consumer is doing the work to provide the values.

[Sam]

I guess one way to think about it is: if you turned a flow into a StateFlow by hand, by collecting values from the flow and setting them on a MutableStateFlow, you'd have to launch a coroutine to do that.

[Joffrey]

I guess it's a similar question to https://kotlinlang.slack.com/archives/C1CFAFJSK/p1644446339713929?thread_ts=1644446339.713929&cid=C1CFAFJSK

[Gabriel Melo]

Ohh, thanks a lot! Now I get it.