I am facing an issue in 1 of my screens, app crash...

# decompose

[Vaibhav Jaiswal]

I am facing an issue in 1 of my screens, app crashes when its minimized, i.e. goes to background

kotlinx.serialization.SerializationException: Serializer for subclass 'class com.medial.app.ui.screens.screens.home.tabs.news.NewsTabComponent$navigateToFilters$1' is not found in the polymorphic scope of 'Function1'.
                                                                                                    Check if class with serial name 'class com.medial.app.ui.screens.screens.home.tabs.news.NewsTabComponent$navigateToFilters$1' exists and serializer is registered in a corresponding SerializersModule.
                                                                                                    To be registered automatically, class 'class com.medial.app.ui.screens.screens.home.tabs.news.NewsTabComponent$navigateToFilters$1' has to be '@Serializable', and the base class 'Function1' has to be sealed and '@Serializable'.

This is the error I’m facing

[Vaibhav Jaiswal]

This is my Screen Config and Component

@Serializable
data class FilterScreen(
    val filters: Pair<List<String>, List<String>>,
    val onFilterSelect: (Pair<List<String>, List<String>>) -> Unit
) : ScreenConfig("Filters")

class FilterComponent(
    componentContext: ComponentContext,
    filters: Pair<List<String>, List<String>>,
    private val onFilterSelected: (Pair<List<String>, List<String>>) -> Unit,
    private val onNavEvent: (AppNavEvents) -> Unit
)

[Vaibhav Jaiswal]

And this is the function mentioned in the error

fun navigateToFilters(){
        val filters = sourceFilters.value.toList() to categoryFilters.value.toList()
        onNavEvent(NewsTabNavEvents.NavigateToFilters(filters, ::onFiltersSelected))
    }

[Arkadii Ivanov]

Can you please show NewsTabNavEvents.NavigateToFilters class?

[Vaibhav Jaiswal]

data class NavigateToFilters(
        val filters: Pair<List<String>, List<String>>,
        val onSelected: (Pair<List<String>, List<String>>) -> Unit
    ) : NewsTabNavEvents

[Arkadii Ivanov]

The issue is because FilterScreen can't be serialized. Pair is not serializable, and you also can't serialize functions.

[Arkadii Ivanov]

I might be wrong about Pair though, it could be handled implicitly by kotlinx-serialization.

[Arkadii Ivanov]

Yeah, Pair is fine as long as all its sub-types are also serializable.

[Vaibhav Jaiswal]

I can split it into two different params no issue there
I cant pass lambda functions ?

[Arkadii Ivanov]

You can't serialize functions (aka lambdas).

[Arkadii Ivanov]

Usually, you can pass lambdas to components at the place when you call constructors.

[Vaibhav Jaiswal]

Any way to navigate to screen which can return result?

[Arkadii Ivanov]

Sure, you can just pass a callback. And call the callback from the child component once the result is available.

[Vaibhav Jaiswal]

Understood, its the interface approach
Thanks for helping

[Arkadii Ivanov]

You can also check the doc section: https://arkivanov.github.io/Decompose/navigation/stack/overview/#delivering-a-result-when-navigating-back

[Vaibhav Jaiswal]

Thanks, Seems I missed this part in the doc