Trying to hoist: ```val radioOptions = listOf("Calls", "Missed", "Friends") val (selectedOption, onO...

# compose

[Dhya Pacifica]

Trying to hoist:

val radioOptions = listOf("Calls", "Missed", "Friends")
val (selectedOption, onOptionSelected) = remember { mutableStateOf(radioOptions[0]) }

Which is from the Compose RadioButton example. Am familiar with hoisting when there is one parameter, but in this case there is the extra parameter onOptionSelected which is throwing me off.

Currently I have the child composable accepting the two parameters like:

@Composable
fun QuestionRadioButtons(
    selectedOption: String,
    onOptionSelected: (String) -> (Unit)
) { ... }

[Kirill Grouchnikov]

What’s the question?

[Dhya Pacifica]

What is onOptionSelected and how is it saved by mutableStateOf ?

[Dhya Pacifica]

I'm not sure why onOptionSelected is needed when selectedOption already contains the state string.

[Kirill Grouchnikov]

Your UI composable gets x as the current state to “display” in the UI, and an onXSomething as the lambda to call upwards when the user interacts with that data display, and that interaction should lead to a state change

[Kirill Grouchnikov]

State update happens outside of your composable, and that place may or may not “accept” the new proposed state

[Kirill Grouchnikov]

See https://developer.android.com/codelabs/jetpack-compose-state#8

[Dhya Pacifica]

Where or how is the onOptionSelected lamba defined?

[Dhya Pacifica]

Thank you!

[Kirill Grouchnikov]

In this particular simplified case, the onOptionSelected is a lambda generated for you with no validation, custom acceptance or rejection, persistence or any other part of it you would have in the real app.

[Kirill Grouchnikov]

For the details on how the tuple is returned by mutableStateOf see the code in https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/[…]c/commonMain/kotlin/androidx/compose/runtime/SnapshotState.kt