Hello all I am having some issues with a recompose not runni

Question

Hello all I am having some issues with a recompose not running when replacing an immutable list

Colton Idle · Answer

< Billy Newman> can you edit your post to put the code in this thread please

Ravi · Answer

Billy Newman · Answer

I have a list of objects that is immutable There is a property that I am using in each object to determine whether or not I want to show the object The parent composable does the filtering ``` Composable fun Stuff state StuffState val values = state values filter it visible == true ValuesContent values ``` ``` Composable fun ValuesContent values List lt Stuff gt values forEach stuff gt show stuff here ``` I modify the state in the viewModel by replacing the entire list with a new list ```val newValues = values toMutableList this should create a new list newValues find update some object let it visible = false state values = newValues``` I am pretty sure if a new list is created a recompose should trigger Is this still true Something else I am doing wrong

Billy Newman · Answer

< Ravi> I get this Assuming you re using the data correctly Compose should just work and you shouldn t have to think any more about it however that is where I am stuck I am using an immutable list and when I replace that list a recompose is not happening

Ravi · Answer

you should consume your `StuffState` as <https developer android com jetpack compose state|State> `collectAsState` or `observeAsState`

Ravi · Answer

you can use `snapshotFlow state values collect `

Billy Newman · Answer

its just a list not coming from flow or livedata still does not fully make sense everything I have read points to using immutable objects I am using an immutable list when anything in that list changes I create a new list far as I can tell a new immutable object in this case a list should recompose such that UI updates accordingly to not show the filtered values

Billy Newman · Answer

``` Composable fun HelloContent name String ``` The name string is immutable here if it changes a recompose will happen to update any views in the HelloContent composable ``` Composable fun HelloContent names List lt String gt ``` The name list here is immutable as well if it changes shouldn t a recompose fire to update the view

Billy Newman · Answer

< Ravi> you were of course right was just having a hard time finding out why as most on internet are incorrect Here from official docs ```Caution Using mutable objects such as ArrayList lt T gt or mutableListOf as state in Compose will cause your users to see incorrect or stale data in your app Mutable objects that are not observable such as ArrayList lt T gt or a mutable data class cannot be observed by Compose to trigger recomposition when they change Instead of using non observable mutable objects we recommend you use an observable data holder such as State lt List lt T gt gt and the immutable listOf ```

Ravi · Answer

<https dev to zachklipp introduction to the compose snapshot system 19cn> check this article

Billy Newman · Answer

Will do thanks for pointing me down the right path