To build a dropdown, I have the following input to...

# compose

[zak.taccardi]

To build a dropdown, I have the following input to a composable:

selectedId: String,
// the `selectedId` will always be in this list
options: List<IdWithDisplayName>

How do I properly use the selectedId to lookup the displayName in the list of options?

IdWithDisplayName.kt

[zak.taccardi]

I think derivedStateOf may be my friend here? https://developer.android.com/jetpack/compose/side-effects#derivedstateof

[mkrussel]

There's no state object to derive from here.

Just remove all the state handling since the state has been hoisted out of MyDropdown. If that lookup is proving too slow, then doing a remember with the selectedId and options as keys could cache the search.

Also may want to consider an ImmutableList so that Compose can optimize.

[Stylianos Gakis]

Are you going to be changing the selectedId inside this composable? Probably not, and if yes, it’d probably be with a lambda to do this further up.
Also exactly as mkrussel says, you don’t have any MutableState to use derivedStateOf, it’s all just parameters coming in the function, so it wouldn’t help you at all.
Simply do a:

val selectedDisplayName = remember(selectedId, options) {
  options.first { it.id = selectedId }.displayName
}

And this should be good enough.