Is there such a thing as a Resource that reinitializes itself if it's closed? I want to store some i...

# arrow

[dave08]

Is there such a thing as a Resource that reinitializes itself if it's closed? I want to store some in a map, close them when unused, re-open them on a new usage.

[simon.vergauwen]

close them when unused

No, that sounds highly mutable and the Map somehow needs to know when it goes out-of-scope.

[simon.vergauwen]

Scala has the concept of HotSwap which I've also ported, but have not bothered bringing to Arrow. It's to basically open and use Resource on rotation.

https://github.com/nomisRev/arrow-fx-coroutines-utils/blob/main/src/commonMain/kotlin/io/github/nomisrev/Hotswap.kt

[dave08]

I have an Android app with a map of state machines handling the state of each item on a list. I was thinking of using resource to initialize and use them in a Compose view and unsubscribe/close them when they go out of view. But when they come back into view, I need to re-initialise them... yeah, I guess that's really mutable, but I'm not sure what I can do otherwise.

[dave08]

open and use Resource on rotation.

If I try to retreive this same resource from the map when it's closed, it'll re-open it?

[simon.vergauwen]

Hmm, so each @Composeable has it's own Resource? A @Composeable can listen to when it gets destroyed, right?

I guess there could be some integration there, using Resource.allocated 🤔 I am not familiar enough with Compose, and it's been a long time since I did Android but it might be possible.

[simon.vergauwen]

Something in @Composeable that doesn't gets retriggered on recomposition, and supports suspend. Is there something like rememberLaunchedEffect where you can attach a Unit key (so it ignores recomposition) and can you then attach some listener to be invoked when they view gets destroyed?

Then it should be possible

[dave08]

There's this: https://developer.android.com/jetpack/compose/side-effects#remembercoroutinescope

[dave08]

The scope seems to get cancelled when not in the UI tree

[dave08]

I guess you mean https://apidocs.arrow-kt.io/arrow-fx-coroutines/arrow.fx.coroutines/-resource/allocate.html

[dave08]

It seems like this is better: https://developer.android.com/jetpack/compose/side-effects#disposableeffect

[dave08]

But it's only in the effect block, and I need to use it outside of that block