Molecule is a library from cashapp, which can write business logic in Compose, and it's also Kotlin Multiplatform project. For more information: https://github.com/cashapp/molecule

https://github.com/cashapp/molecule

implementation("io.github.aleyn97:molecule-util:x.y.z")

MoleculeUtil is an extension library for Molecule. It has the same functionality as PreCompose, but integrating the org.jetbrains.kotlin.native.cocoapods plugin with the IOS platform may cause conflicts. MoleculeUtil handles conflict issues

You can write a Presenter like this:

@Composable
fun CounterPresenter(
    action: Flow<CounterAction>,
): CounterState {
    var count by remember { mutableStateOf(0) }

    action.collectAction {
        when (this) {
            CounterAction.Increment -> count++
            CounterAction.Decrement -> count--
        }
    }

    return CounterState("Clicked $count times")
}

in your Compose UI, you can use this CounterPresenter with rememberPresenter

val (state, channel) = rememberPresenter { CounterPresenter(it) }

state is the instance of CounterState, which return by CounterPresenter, and channel is the instance of Channel<CounterEvent>, you can send event to CounterPresenter by channel.trySend(CounterEvent.Increment)

The molecule scope and the Event Channel will be managed by the ViewModel, so it has the same lifecycle as the ViewModel.

You can nest your Presenter by using rememberNestedPresenter

If you prefer using State Action, you can write a Presenter like this:

@Composable
fun CounterPresenter(): CounterState {
    var count by remember { mutableStateOf(0) }
    return CounterState("Clicked $count times") {
        when (it) {
            CounterAction.Increment -> count++
            CounterAction.Decrement -> count--
        }
    }
}

in your Compose UI, you can use this CounterPresenter with producePresenter

val state by producePresenter { CounterPresenter() }