created a Compose Multiplatform project form <Compose Multiplatform Wizard>. When i ran it on ios si...

# compose-ios

[Shoaib khalid]

created a Compose Multiplatform project form Compose Multiplatform Wizard. When i ran it on ios simulator it called the ComposeUIViewController callback twice, though MainViewController called only once.
I've following code in my composeApp/src/iosMain/kotlin/main.kt

fun MainViewController(systemAppearance: (isLight: Boolean) -> Unit): UIViewController {
    println("Outside ComposeUIViewController")

    return ComposeUIViewController {
        println("Inside ComposeUIViewController")
        App() }
}

below is the output.

[Alejandro Rios]

Possibly related :
https://kotlinlang.slack.com/archives/C0346LWVBJ4/p1694447536035539

[Shoaib khalid]

Thanks @Alejandro Rios but in my case MainViewController is called once but ComposeUiViewController is called twice which is weird. I don't know if it's default behaviour or something else.

[Pablichjenkov]

I think you are printing any time it recomposes. In compose a Composable down the tree can perfectly trigger recomposition in its parents scope.

[Shoaib khalid]

@Pablichjenkov App() composable is empty so there's no chance it's gonna recompose.

[Shoaib khalid]

@Composable
internal fun App(){
}

[Shoaib khalid]

whenever i run app it calls ComposeUiViewController lambda twice.

[Pablichjenkov]

Yeah sounds like it shouldn't do it but internally it may trigger recomposition. I started noticing that I believe after Safe area modifiers were added

[Pablichjenkov]

Perhaps they need 2 compositions to compute some layout values. But let's wait if someone comes up with a better response

[Shoaib khalid]

if that's the case it'll be a big disappointment as it's so weird.

[Shoaib khalid]

Is it the same case with your compose multiplatform project?

[Pablichjenkov]

I will let you know but most likely. Far from the Mac now I will verify later. But I believe last time I checked same thing. I don't care much about recompositions to be honest. Although I agree that minimizing them is important.

[mohamed rejeb]

what about priniting inside a LaunchedEffect it's more important but having 2 recompositions is not a big deal, the second recomposition could be ignored by childs.

[Arkadii Ivanov]

There shouldn't be any issues as long as there is only one composition. I.e. all remember-ed values are retained, DisposableEffect.onDispose is not called, etc.

[Pablichjenkov]

So yes Shoaib just checked and on my side, I see the same behaviour. Notice it only happens the first time the App launches. Subsequent calls of ViewDidDisappear/ViewDidAppear don’t print anything.
LaunchEffect printed only once as expected too.

[Shoaib khalid]

Resolved https://github.com/JetBrains/compose-multiplatform/issues/3778

[Pablichjenkov]

Ah great 😃