class Presenter(var counter: Int = 0)

// Retain an instance in an Activity:
class CounterActivity : AppCompatActivity() {
    private val presenter: Presenter by retain { Presenter() }
}

// Retain an instance in a Fragment:
class CounterFragment : Fragment() {
    private val presenter: Presenter by retain { Presenter() }
}

// Share an instance between Fragments scoped to the Activity
class CounterFragment : Fragment() {
    private val sharedPresenter: Presenter by retainInActivity { Presenter() }
}

// Share an instance between Fragments scoped to the NavGraph
class CounterFragment : Fragment() {
    private val presenter: Presenter by retainInNavGraph(R.navigation.nav_graph) { Presenter() }
}

@Composable
fun CounterScreen() {
    // Scope to LocalViewModelStoreOwner (default)
    val presenter = retain { Presenter() }

    // Scope to ComponentActivity (Android)
    val activityPresenter = retainInActivity { Presenter() }

    // Scope to a specific ViewModelStoreOwner (e.g. NavBackStackEntry)
    val navBackStackEntry: NavBackStackEntry // Find NavBackStackEntry
    val scopedPresenter = retain(owner = navBackStackEntry) { Presenter() }
}

@Composable
fun CounterScreen() {
    val presenter = retain { entry: RetainedEntry ->
        Presenter()
    }
    // ...
}

class CounterFragment : Fragment() {
    private val presenter: Presenter by retain { entry -> 
        Presenter(counter = entry.savedStateHandle.get<Int>("count") ?: 0)
    }
    // ...
}

class Presenter(scope: CoroutineScope) { /* ... */ }

class SampleFragment : Fragment() {
    private val presenter: Presenter by retain { entry -> 
        Presenter(scope = entry.coroutineScope)
    }
    // ...
}

class ResourcePresenter : AutoCloseable {
    override fun close() {
        // Automatically called when the host ViewModel is cleared
    }
}