Hi again, So say I were to have a data structure ...

# compose-android

[Rohan]

Hi again,

So say I were to have a data structure like so:

data class commentNode (
    var children: MutableList<CommentNode>? = mutableListOf(),
    var collapsed: Boolean = false
) {}

And all of this is contained in a variable that looks something like so:

var tree: MutableList<CommentNode> = mutableListOf()

As you can imagine, this would produce a nested tree-like structure.
So, using state, how would I trigger recomposition when changing the value collapsed in any nested CommentNode?

Any help is appreciated :)

[alaershov]

Do you want your CommentNode to implement State in a custom way and notify its observers about changes?
I'd suggest a different approach and make your CommentNode immutable, and just pass it as a regular @Stable class. Then just pass it to a composable function, and it will recompose on any change. Of course, you'd have to "change" it using copy()

[Rohan]

That's an interesting idea, but if I change a nested comment node inside a mutable list using copy(), would that still cause the screen to recompose?

[alaershov]

no, regular mutable collections aren't observable in Compose. You should use ImmutableList<CommentNode> if you take immutable approach, or mutableStateListOf<CommentNode>() if you insist on mutability

[alaershov]

I would probably make it like this:

data class CommentNode (
    val children: ImmutableList<CommentNode> = persistentListOf(),
    val collapsed: Boolean = false
)

[Rohan]

Thank you so much! This works perfectly 😄 I've spent a while trying to get this working so thanks!