In my composable I have this ```val sizeOfSomeSortaNedtedThing = myScreenState.listOf20Items.fla...

# compose

[Colton Idle]

In my composable I have this

val sizeOfSomeSortaNedtedThing =
    myScreenState.listOf20Items.flatMap { it.subListOf10Items }.flatMap { it.anotherSubListOf10Items }
        .filter { it.isDone }.size

Should I try to have this remembered? Should I just move this into myScreenState as a top level field thats calculated before-hand?

[Francesc]

Profile to determine if it's an issue then take any necessary action

[Stylianos Gakis]

At the same time, wrapping this into a remember is so simple that you might as well do it.

val sizeOfSomeSortaNedtedThing = remember(myScreenState.listOf20Items) {
    myScreenState.listOf20Items.flatMap { it.subListOf10Items }.flatMap { it.anotherSubListOf10Items }
        .filter { it.isDone }.size
}

[Francesc]

At the same time, a remember has a cost associated to it, so you should not be remembering stuff willy-nilly

[Tim McCormack]

What sort of cost? Memory, cache key recomputation?

[Francesc]

this explains much better than I possibly could https://medium.com/androiddevelopers/under-the-hood-of-jetpack-compose-part-2-of-2-37b2c20c6cdd

[Tim McCormack]

So it looks like you can replace a calculation with a cache key computation and equality check, at the expense of storing a potentially redundant/unused copy of the data (depending on your use case).

[Tim McCormack]

(and the cache is of size 1)

[Colton Idle]

@Stylianos Gakis any reason why you chose to remember(myScreenState.listOf20Items) ? and not just have an empty remember

[Stylianos Gakis]

Yes, if listOf20Items changes your remember will not re-run and it will simply keep the result of whatever the first result it ever got was.

[Stylianos Gakis]

So, maybe you asking this question maybe hints towards what the rest of the folks are saying. Maybe it’s a better idea not to do anything special with it unless it’s a real performance issue. Since if you do try to do something with it (like remembering it) you risk of the having correctness bugs if you do it wrong as opposed to have some potentially non-impactful performance issues. And having correctness problems is much much worse in this case then

[Colton Idle]

Gotcha. Cool. I've never used a remember with an arg hence why I asked. 😄

[Stylianos Gakis]

That sounds a tiny bit concerning 😄
Either you’re not using remember a whole lot, or there’s a good chance some of your remembers are resulting in you showing some stale data 👀

[Colton Idle]

Yeah, I mean i only use remember when i have stateful composables which is infrequent

[Colton Idle]

but i just go by the examples that compose has

[Colton Idle]

but yeah. 4 apps shipped to prod. no perf or staleness issues here. so im doing something right. hahahah

[Colton Idle]

over 1 million happy-ily installed users 👌

[Tim McCormack]

So far I've only encountered one example in the docs that shows remember being used with keys. :-/