How to send the cancelation result?

[margarita-v]

Now it's possible to use resultNavigator.navigateBack for sending confirmation result from screen. Is there any opportunity to send the cancelation result when the result screen composable is gone in order to handle both results in the same callback of recipient screen?
For example:

@Destination
@Composable
fun FeedScreen(
    openForResultClicked: () -> Unit,
    onResult: (Boolean) -> Unit,
    resultRecipient: ResultRecipient<ResultScreenDestination, Boolean>
) {
    resultRecipient.onResult { succeed ->
        onResult(succeed)
    }
    // open screen for result
}

@Destination
@Composable
fun ResultScreen(
    navBackStackEntry: NavBackStackEntry,
    resultNavigator: ResultBackNavigator<Boolean>
) {
   // Doesn't work: when the ResultScreen composable is gone, I'd like to send this cancelation result in order to handle in the same `onResult` callback of FeedScreen
    DisposableEffect(key1 = Unit) {
        onDispose {
            resultNavigator.setResult(false)
        }
    }
    Box(modifier = Modifier.fillMaxSize()) {
        Button(
            onClick = {
                // the confirmation result works when action is performed
                resultNavigator.navigateBack(true)
            },
            modifier = Modifier.align(Alignment.Center)
        ) {
            Text(textAlign = TextAlign.Center, text = "Success!")
        }
    }
}

This DisposableEffect for ResultScreen doesn't work too:

    DisposableEffect(key1 = Unit) {
        val observer = LifecycleEventObserver { source, event ->
            when (event) {

                Lifecycle.Event.ON_DESTROY -> {
                    resultNavigator.setResult(false)
                }

                else -> Unit
            }
        }

        navBackStackEntry.lifecycle.addObserver(observer)

        onDispose {
            navBackStackEntry.lifecycle.removeObserver(observer)
        }
    }

Is there any best practice to solve it or should I use different callbacks for cancelation based on composable lifecycle and confirmation based on action?

[raamcosta]

Hi @margarita-v ! Thank you again for reporting! :)

I remember thinking if this would ever be helpful when I was implementing the nav result feature. Turns out it is.

Would this work for your use case?

• If ResultScreen becomes visible and after that, the FeedScreen becomes visible again and no value is received, then we consider it canceled. This would be done by the library, and the result received on onResult would be a wrapper to the current value which would allow us to check if nav result was canceled or there is actually a value:

sealed interface NavResult<out R> {
    object Canceled: NavResult<Nothing>
    data class Value<R>(val value: R): NavResult<R>
}

//...
    resultRecipient.onResult { confirmed ->
        when (confirmed) {
            is NavResult.Canceled -> println("canceled!!")
            is NavResult.Value -> if (confirmed.value) {
                navigator.navigate(SomeDestination)
            }
        }
    }

[margarita-v]

I think it would be perfect 👍

[raamcosta]

Hey @margarita-v !

So the new 1.3.5-beta release contains this new enhancement and deprecates the old onResult to replace it with onNavResult.
Please try it and let me know if that works well for you! 🙂

[margarita-v]

Thank you, now it works perfectly 🔥