*[*:white_check_mark: SOLVED] *Subject*: `remember...

# compose

[theapache64]

[✅ SOLVED]
Subject: rememberUpdateState

I’ve seen most of the @Composables are using rememberUpdateState before invoking a lambda.
For eg, BackHandler internally calling rememberUpdateState on onBack lambda, clickable modifier calls on onClick lambda.
Does that mean we should wrap all lambda with rememberUpdateState before invoking ? 🤔
If that’s the case, why can’t compiler do it for us?

#possibly_a_stupid_question

[Albert Chang]

Have you checked the doc? I think it explains when you need to use rememberUpdatedState quite clearly.

[theapache64]

@Albert Chang Yes. I already read that doc. That explains one of the usecases of rememberUpdateState with LaunchedEffect. But what am asking is, basically we use rememberUpdateState to get the latest value (or to avoid stale value). Is there a scenario where we need to access the stale value? 🤔

[Albert Chang]

The point is whether there is a long-living lambda (or function) that captures the value. If there isn't such a lambda, there is no need to use rememberUpdatedState.

[theapache64]

Hmm. but Lambdas are mostly long-living functions or mostly used at later time (or after the composition). For example, onClick, onBack etc.
So lambas without rememberUpdatedState should be very rare?

[Albert Chang]

No, most lambdas are not long-living. In a composable function, if the dependencies of a lambda (i.e. the variables it captures) change, a new lambda instance will be created.

[Albert Chang]

By saying long-living I mean it survives recomposition.

[theapache64]

okay, so basically, I only need to use rememberUpdatedState if and only if am accessing a lambda in an area where recomposition can’t be reached. For example, remember , LaunchedEffect, etc.. is that what you’re saying ?

[Albert Chang]

Yep. But for remember, it's better to just use it as a key.

[theapache64]

ahaa.. got it.

[theapache64]

so here they used rememberUpdateState because its easier better than recreating the DisposableEffect ?

[theapache64]

i mean, if the code is something like this

[theapache64]

they don’t need rememberUpdateState here.

[Albert Chang]

Yeah OnBackPressedDispatcher is designed that way.

[theapache64]

Got it. thank you so much for bearing with me 😄

[rocketraman]

See also related DX feature request: https://issuetracker.google.com/issues/217570480