Hello there! I’m trying to write helper function f...

# compose

[yuriy.stetsyk]

Hello there!
I’m trying to write helper function for Flow<T>.collectAsSnackBarStateWithLifecycle(...): State<AppSnackBarData?>
AppSnackBarData is my custom SnackBar description. It will be shown until produced state emits null
The goal is to produce state that emits null after short period of time, to dismiss snack bar.
Details it thread

Would appreciate any tips/improvements, thanks!

[efemoney]

https://kotlinlang.slack.com/archives/C0346LWVBJ4/p1681675445094099?thread_ts=1681635951.075489&cid=C0346LWVBJ4

[yuriy.stetsyk]

I took inspiration from implementation of Flow<T>.collectAsStateWithLifecycle(...): State<T>
My current version looks like this

@Composable
fun <T> Flow<T>.collectAsSnackBarStateWithLifecycle(
    snackbarDuration: SnackbarDuration = SnackbarDuration.Short,
    accessibilityManager: AccessibilityManager? = LocalAccessibilityManager.current,
    lifecycleOwner: LifecycleOwner = LocalLifecycleOwner.current,
    minActiveState: Lifecycle.State = Lifecycle.State.STARTED,
    context: CoroutineContext = EmptyCoroutineContext,
    mapToSnackbarData: (T) -> AppSnackbarData?,
): State<AppSnackbarData?> = collectAsSnackBarStateWithLifecycle(
    snackbarDuration = snackbarDuration,
    accessibilityManager = accessibilityManager,
    lifecycle = lifecycleOwner.lifecycle,
    minActiveState = minActiveState,
    context = context,
    mapToSnackbarData = mapToSnackbarData,
)

@Composable
fun <T> Flow<T>.collectAsSnackBarStateWithLifecycle(
    snackbarDuration: SnackbarDuration,
    accessibilityManager: AccessibilityManager?,
    lifecycle: Lifecycle,
    minActiveState: Lifecycle.State = Lifecycle.State.STARTED,
    context: CoroutineContext = EmptyCoroutineContext,
    mapToSnackbarData: (T) -> AppSnackbarData?,
): State<AppSnackbarData?> {
    return produceState<AppSnackbarData?>(
        null,
        this,
        snackbarDuration,
        accessibilityManager,
        lifecycle,
        minActiveState,
        context,
        mapToSnackbarData,
    ) {
        suspend fun transformAndEmit(t: T) {
            val data = mapToSnackbarData(t)
            [e-mail] = data

            if (data != null && data.style !is AppSnackbarStyle.Progress) {
                delay(snackbarDuration.toMillis(accessibilityManager))
                [e-mail] = null
            }
        }

        lifecycle.repeatOnLifecycle(minActiveState) {
            if (context == EmptyCoroutineContext) {
                [e-mail] { // Using collectLatest to cancel delay in transformAndEmit
                    transformAndEmit(it)
                }
            } else withContext(context) {
                [e-mail] {
                    transformAndEmit(it)
                }
            }
        }
    }
}

Main usage would look as follows

val snackBarData by alerts.collectAsSnackBarStateWithLifecycle { alert -> alert.asSnackBarData() }

Though it behaves as expected in my tests, but I have a few concerns
1. mapToSnackbarData lambda, should it be remembered before passing it to collectAsSnackBarStateWithLifecycle, as it is one of the keys for produceState
2. Usage of collectLatest, I think it it safe to use it, but not sure