Hi Fellas, I have been facing some issue while d...

# decompose

[Anshulupadhyay03]

Hi Fellas,

I have been facing some issue while doing navigation.push to a screen on iOS. In Android on item click I am doing navigation.push to detailScreen which is working fine however the same code(as i am using compose multiplatform for both iOS and Android ) is not navigating to the detailScreen for iOS. I have debugged that for iOS it doesn't call onComplete callback but for Android it does.
decompose lib version : decompose = "3.0.0-alpha07"

private fun onMovieSelected(movieId: Int) {
        println("item onMovieSelected-$movieId")
        navigation.push(Configuration.Details(movieId), onComplete = {
            println("Ansh: isMovieSelected ")
        })
    }

main class for iOS

fun MainViewController(lifecycle: LifecycleRegistry) = ComposeUIViewController {
    CompositionLocalProvider{
        val root = MovieBuffRootImpl(DefaultComponentContext(lifecycle = lifecycle))
        App(root)
    }
}

MovieBuffRootImpl :
https://pastebin.com/rTBU8Zax

[Arkadii Ivanov]

There are not enough details to say what's wrong. The related code is the same for all platforms, so it should work fine. A reproducer could help.

[Anshulupadhyay03]

@Arkadii Ivanov thanks for your response. I have edited the question with more details . let me know if you want more info.

[Arkadii Ivanov]

Thanks! I don't see any problems with the code. The completion callback should always be called. Would it be possible to create a reproducer?

[Anshulupadhyay03]

@Arkadii Ivanov If you dont see any basic issue the code then i will have to do some debugging from my end and come back to you with more concrete information.

[Arkadii Ivanov]

Yeah, the code looks good. There might be a bug in Decompose, though. Feel free to share a reproducer.

[Arkadii Ivanov]

Actually, I have just realised that you are creating the root component and the component context incorrectly. You have to create those outside of Compose. Please see the doc: https://arkivanov.github.io/Decompose/component/overview/#root-componentcontext-in-jetpackjetbrains-compose

[Anshulupadhyay03]

@Arkadii Ivanov Thanks for the suggestion however i found the solution bit different. I moved the code out of the compose but that did not work either but when I pass the LifecycleRegirty() inside the ComponentContext rather than taking it from the iOS code, it started working. But I am not sure what was going wrong with it . Please explain if you understood.

This is what works :

fun MainViewController(lifecycle: LifecycleRegistry) = ComposeUIViewController{
    val root = MovieBuffRootImpl(DefaultComponentContext(lifecycle = LifecycleRegistry()))
    App(root)
}

This is the ios code where I was passing lifecycle instance

struct ComposeView: UIViewControllerRepresentable {
    private var lifeCycleHolder:LifeCycleHolder {LifeCycleHolder()}
    func makeUIViewController(context: Context) -> UIViewController {
        Main_iosKt.MainViewController(lifecycle:lifeCycleHolder.lifecycle)
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {}
}

struct ContentView: View {
    var body: some View {
        ComposeView()
                .ignoresSafeArea(.keyboard) // Compose has own keyboard handler
    }
}

and here it is the LifecycleHolder class

class LifeCycleHolder : ObservableObject {
    
    let lifecycle:LifecycleRegistry
    
    init(){
        lifecycle = LifecycleRegistryKt.LifecycleRegistry()
        
        lifecycle.onCreate()
    }
    
    deinit {
        lifecycle.onDestroy()
    }

}

[Arkadii Ivanov]

Thanks! Your MainViewController function appears to be incorrect as well. You shouldn't call MovieBuffRootImpl(DefaultComponentContext(lifecycle = LifecycleRegistry())) inside a Composable function, as explained in the docs. Keep in mind that ComposeUIViewController {} lambda block is Composable. You can do something like this:

fun MainViewController(lifecycle: Lifecycle): UIViewController {
  val root = MovieBuffRootImpl(DefaultComponentContext(lifecycle = lifecycle))
  return ComposeUIViewController { App(root) }
}

[Anshulupadhyay03]

@Arkadii Ivanov i am not sure if you understood what I mentioned in my above reply. It is possible that my MainViewController is not correct however moving root outside of ComposeUIViewController did not work either. What actually worked was passing LifecycleRegistry() instead of lifecycle passed from my iOS lifecycle MainViewController(lifecycle: Lifecycle) and I am clueless what was the problem as earlier same code was working fine for older versions of decompose.

This is the code that works

fun MainViewController(): UIViewController {
    val root = MovieBuffRootImpl(DefaultComponentContext(lifecycle = LifecycleRegistry()))
    return ComposeUIViewController {
        App(root)
    }
}

[Arkadii Ivanov]

I can't tell what was the problem without a reproducer, unfortunately. But with your current approach you should also control LifecycleRegistry somehow. Otherwise your components won't receive any lifecycle events.

[Anshulupadhyay03]

@Arkadii Ivanov Yes makes sense ....You can checkout this https://github.com/youranshul/KmmMovieBuff/tree/decompose_navigation ...If you want I can share the api_key separately as this is just a learning app.

[Arkadii Ivanov]

Thanks for the reproducer! Turned out our LifecycleHolder is garbage collected, and so the lifecycle is destroyed.

If you want to use this "Holder" pattern, then please follow this doc: https://arkivanov.github.io/Decompose/getting-started/quick-start/#ios-with-swiftui-without-the-experimental-applicationlifecycle.

Alternatively, since you have only one root component and it lives in the app scope, you can use ApplicationLifecycle instead: https://arkivanov.github.io/Decompose/getting-started/quick-start/#ios-with-swiftui-with-the-experimental-applicationlifecycle

[Anshulupadhyay03]

@Arkadii Ivanov Thanks for the response. Is this happening because I bumped up my decompose library to use it for wasm as in earlier version which I used was all good and it was working fine ?

[Arkadii Ivanov]

I don't think so. SwiftUI views are structs, a view struct is recreated on each view update. So any class stored as a property is also recreated, and the previous instance is deallocated. Storing objects in a view requires some extract care, e.g. using StateObject. Or just using the vanilla UIApplicationDelegate as described here. Or just use the new ApplicationLifecycle , as it should work perfectly fine for your use case (one component hierarchy for the entire app).

[Anshulupadhyay03]

@Arkadii Ivanov Thanks a lot!