`remember {}` saves X for recomposition but when c...

# compose

[Marko Novakovic]

remember {} saves X for recomposition but when composable leaves the screen X is forgotten. if I want to save X even when composable leaves the screen I should use rememberSaveable {} right? it seems weird because concept of rememberSaveable {} is for surviving recreating but composable leaving the screen is not recreation. conceptually not the same. should I use rememberSaveable {} or there is some other way to handle this use case?

[knthmn]

IMO it is more logical to hoist the state to a place with the lifetime you want.

[Marko Novakovic]

@knthmn I understand and I agree. BUT. what if you don’t need/want that state hoisted? let’s say you have list of items you want to select. yes, you probably need to do something with those items inside ViewModel or something and in that case you can make composables(items) in the list stateless (implementation differs from use case to use case) but what if you don’t need these items inside ViewModel? maybe your use case is so simple and you would introduce ViewModel just for saving checked state? this is all maybe and probably not good example but I hope you get a point

[Arkadii Ivanov]

You can try Decompose, it works exactly how you expect.

[Colton Idle]

@Marko Novakovic not an expert, but "if i want to save x even when composable leaves the screen" do you mean when you use it in a LazyColumn?

Composables leaving the screen AFAIK don't lose their state. It's only if it's in a lazy container will it lose it's state. And in that case, you want to do what the first comment said and hoist the state up.

Again, not an expert and so I could be completely wrong. Adam Powell could probably clear it up when he wakes up, BUT it might make sense for you to define "leaves the screen". Do you navigate to another screen? Do you mean scrolling off the screen in a Column? Do you mean scrolling off the screen in a lazy column? Do you mean off the screen as in backgrounding the app, and then process death hits. etc.

[knthmn]

@Marko Novakovic can you provide a concrete example on what you want stored?

[Adam Powell]

all the viewModel composable is doing is hoisting your state into LocalViewModelStoreOwner.current for you

[Adam Powell]

the lazy layouts do indeed have items leave the composition entirely when they're no longer visible, so yes, if you don't hoist state somewhere, it won't stick around.

[Marko Novakovic]

@knthmn I don’t have an example. I played around with it and was wondering. conceptually didn’t make sense

[Marko Novakovic]

@Adam Powell thanks

[Andrey Kulikov]

rememberSaveable can also be used inside LazyColumn items for not loosing the local state when the item is scrolled off the screen(for example for checked state as you mentioned). so activity recreation is just one of the use cases of rememberSaveable

[Marko Novakovic]

@Andrey Kulikov that’s the answer I was looking for. thanks!

[Marko Novakovic]

@Andrey Kulikov and that was my test case, store variable with remember {} and rememberSaveable {} and scroll item off the screen, than bring it back to see what’s going on