State Management — KMP

State as a Data Class

In the KMP / Decompose path, state is a plain data class — no marker interface required.

data class HomeState(
    val title: String = "",
    val isLoading: Boolean = false,
)

Holding and Updating State

BaseComponent provides componentState: MutableStateFlow<VS> to hold the component's state.

Update state by replacing the value directly:

componentState.value = componentState.value.copy(title = "new")

Or use the update helper from app.futured.arkitekt.decompose.ext:

update(componentState) { copy(title = "new") }

Exposing State

Expose state to the UI as a read-only StateFlow:

class HomeComponent(
    componentContext: AppComponentContext,
) : BaseComponent<HomeState, HomeUiEvent>(componentContext, HomeState()) {

    val state: StateFlow<HomeState> = componentState
}

asStateFlow Helper

BaseComponent provides an asStateFlow() extension on Flow<VS> that converts a Flow to a StateFlow within the component's coroutine scope. This is useful when you want to derive state from another flow:

val derivedState: StateFlow<DerivedState> = someFlow
    .map { DerivedState(it) }
    .asStateFlow(SharingStarted.WhileSubscribed(5_000))

Observing State in Compose

@Composable
fun HomeScreen(component: HomeComponent) {
    val state by component.state.collectAsState()

    if (state.isLoading) {
        CircularProgressIndicator()
    } else {
        Text(state.title)
    }
}