hey guys since `derivedStateOf` should be always w...

# compose

[deviant]

hey guys
since derivedStateOf should be always wrapped into remember, i decided to make this helper

@Composable
fun <T> rememberDerived(calculation: () -> T) = remember {
    derivedStateOf(calculation)
}

do you see any issues with it?

[deviant]

ok. it doesn't work as i was expecting!
the state isn't deriving. not sure why, probably some internal compose magic

[deviant]

also i saw somewhere in chats that derivedStateOf should be always wrapped

[Stylianos Gakis]

Yes you do need to remember your derivedStateOf calls. I don’t know about the function above though, if compose can still do proper tracking of what is read inside the derivedStateOf to only recompose when it needs to. For one maybe this function is introducing a new recomposition scope? How does it work if you make it inline, does it do what you expect? Just a wild guess though.
I’d personally go for simple remember { derivedStateOf {} } since sometimes you do want to pass some things as keys to the remember function if they’re not state objects. Since derivedStateOf only knows how to read and automatically keep up to date with state objects, not anything you put in there.

[FunkyMuse]

https://kotlinlang.slack.com/archives/CJLTWPH7S/p1659521757388299?thread_ts=1659515103.204379&cid=CJLTWPH7S

This is changing because the highPriorityKeyWords changes and the derived is recalculated

[Stylianos Gakis]

Regarding the docs sample, do you have a link to it?
I'd guess the todoTasks is a state object while highPriorityKeywords is not a state object, hence you'd need to do that. But I'd love to see the docs link

[shikasd]

A) you need to remember derived state object, otherwise it will create a new state each composition
B) if you can confirm that your helper doesn't work, please file a bug, this usage looks legit to me

[Sean McQuillan [G]]

very minor drive by comment - you can make @Composable funs inline, which has the effect of making them inline, and never-skippable

[Sean McQuillan [G]]

this is already never-skippable due to return value

[deviant]

the proposed helper function seems works fine. i added optional key param to pass into remember. the bug i observe is coming from somewhere else. and i can't reproduce it on hello world project (my widget isn't being updated despite the recomposition is being triggered). will file a bug when have an evidences