<@UHAJKUSTU> iOS App's nav backstack is getting cl...

# decompose

[Vaibhav Jaiswal]

@Arkadii Ivanov iOS App's nav backstack is getting cleared when device theme is changed
I remember this was fixed on Android with the discardSavedState param

Code in Thread

[Vaibhav Jaiswal]

object MedialApp {

    private val deeplink = MutableStateFlow<String?>(null)

    /**
     * Call from iOS
     */
    fun setUpDeeplink(deeplink: String?) {
        this.deeplink.update { deeplink }
    }

    @OptIn(ExperimentalDecomposeApi::class, ExperimentalComposeApi::class)
    fun viewController(): UIViewController {

        return ComposeUIViewController(
            configure = {
                onFocusBehavior = OnFocusBehavior.DoNothing
                opaque = false
            },
        ) {
            val permissionController = remember { PermissionsController() }
            val deeplink by this.deeplink.collectAsState()
            val backDispatcher = BackDispatcher()
            val rootComponent = RootComponentImpl(
                componentContext = DefaultComponentContext(
                    lifecycle = ApplicationLifecycle(),
                    backHandler = backDispatcher
                ),
                deeplink = deeplink,
                permissionController = permissionController
            )
            PredictiveBackGestureOverlay(
                backDispatcher = backDispatcher, // Use the same BackDispatcher as above
                backIcon = { progress, _ ->
                    PredictiveBackGestureIcon(
                        imageVector = Icons.Default.ArrowBack,
                        progress = progress,
                    )
                },
                modifier = Modifier.fillMaxSize(),
            ) {
                MedialApp(
                    component = rootComponent,
                    modifier = Modifier.fillMaxSize()
                )
            }
        }
    }

}

[Arkadii Ivanov]

Could you please elaborate, what's the actual issue?

[Vaibhav Jaiswal]

If I change the device theme from light -> dark and vice versa
The app seems to start again from the 1st screen

[Arkadii Ivanov]

Got it, and you want to prevent it, right?

[Vaibhav Jaiswal]

yes

[Arkadii Ivanov]

Ok. I'm not a pro iOS dev, so I might be wrong. I think this happens because the app is restarted and the state is not saved. I would first check if there is any way of preventing the app from being restarted. But if there is not, as a last resort you can save and restore the state manually. See here: https://github.com/arkivanov/Decompose/blob/0708bbda5bca9df0669944d8893736353e418c43/sample/app-ios/app-ios/app_iosApp.swift#L39

[Vaibhav Jaiswal]

Thanks, how can i do this in the Kotlin side?

[Arkadii Ivanov]

There are two parts, Swift-side and Kotlin-side. You can check the sample.

Also, I would try looking for another solution first. Maybe there is a configuration flag to prevent the restart, or something similar.

[Vaibhav Jaiswal]

I'll take a look, thanks

[Vaibhav Jaiswal]

@Arkadii Ivanov for this solution, in the sample the rootComponent creation is on the Swift Side, how to do this when everything is in shared Compose side?
I'm not able to find anything on stopping ios app from restarting

[Arkadii Ivanov]

I don't think it's possible to implement everything in Kotlin. I suggest to at least create DefaultComponentContext on the Swift side. I would also create the RootComponent on the Swift side, as there might be iOS specific dependencies.