Hi! How can we use ON_PAUSE and ON_RESUME lifecycl...

# compose-ios

[Ahmad Hassan]

Hi!
How can we use ON_PAUSE and ON_RESUME lifecycle functions in Compose Multiplatform as in Jetpack Compose in Android?

[Ivan Matkov]

androidx.lifecycle.* is currently Android-only

[Ahmad Hassan]

Any hint at how we can do this?

[Ivan Matkov]

1.5.10-beta01 adds view controller lifetime hooks - https://github.com/JetBrains/compose-multiplatform-core/pull/779

[Arkadii Ivanov]

This would require support from a navigation library. Decompose provides this support, and I think Decompose-Router as well. Maybe other navigation libraries have it as well, not sure.

[Arkadii Ivanov]

If you don't need navigation for some reason (e.g. your app has only one screen), then you could try using Essenty directly.

[Ahmad Hassan]

Thank you for the response.
Can you please suggest how can I use it in Compose? Any sample?

[Arkadii Ivanov]

There are samples and docs if you follow the links for the libraries. But there are no samples I'm aware of for just using the Essenty Lifecycle, without any library. But you can check the readme, it's pretty easy.

[Ahmad Hassan]

https://github.com/arkivanov/Essenty#lifecyle

I want to use Essenty, but there’s no sample here.

[Ahmad Hassan]

@Ivan Matkov
How can we use these hooks?
Can you please share any sample?

[Arkadii Ivanov]

With Essenty you can use LifecycleRegistry . Then just override applicationDidBecomeActive , applicationWillResignActive and applicationWillTerminate and drive the lifecycle. Take a look here.

Then you can create a composition local for Lifecycle so that it's available in every Composable.

[Arkadii Ivanov]

Or if you are using ComposeUIViewController {} function, then there is now the delegate property that can be used instead.

[Ahmad Hassan]

Thank you for the response.
How can we use this delegate property?

[Arkadii Ivanov]

I guess something like this:

ComposeUIViewController {
    val lifecycle = remember { LifecycleRegistry() }

    delegate = 
        object : ComposeUIViewControllerDelegate {
            override fun viewWillAppear() {
                lifecycle.resume()
            }

            override fun viewDidDisappear() {
                lifecycle.stop()
            }
        }

    // The rest of the code
}

Though, I don't see any callback equivalent to onDestroy. In Swift we have deinit. So perhaps you could create and control the lifecycle in Swift and then just pass it to Compose and make it available with a composition local.

Or, if you have just one Composable for the entire app, then you can implement UIApplicationDelegate instead, which gives applicationWillTerminate callback.

[Ahmad Hassan]

Thanks!
Let me check