Refactor rename rememberViewModel to be architecture agnostic

README.md

@@ -145,24 +145,23 @@ fun ListDetailScreen() {
   }
 }
 
-// If you want your view-model to survive config changes 🔁, make it implement the [Instance] interface
-class ListViewModel : InstanceKeeper.Instance
-
-// If you want your state to survive process death ☠️, derive your initial state from [SavedStateHandle] 
-class DetailViewModel(savedState: SavedStateHandle, detail: String) : InstanceKeeper.Instance {
-  private val initialState: DetailState = savedState.get() ?: DetailState(detail)
-  private val stateFlow = MutableStateFlow(initialState)
-  val states: StateFlow<DetailState> = stateFlow
-}
-
 @Composable
 fun DetailsScreen(detail: String) {
-  // Scope your view models to screen so that they get cleared when user leaves the screen 
-  val viewModel: DetailViewModel = rememberViewModel { savedState -> DetailViewModel(savedState, detail) }
+  // 📦 Scope an instance (a view model, a state-holder or whatever) to a route with [rememberOnRoute] 
+  //   1. Makes your instances survive configuration changes (on android) 🔁
+  //   2. Holds-on the instance as long as it is in the backstack 🔗
+  val instance: DetailInstance = rememberOnRoute { savedState -> DetailInstance(savedState, detail) }
 
-  val state: DetailState by viewModel.states.collectAsState()
+  val state: DetailState by instance.states.collectAsState()
   Text(text = state.detail)
 }
+
+// If you want your state to survive process death ☠️ derive your initial state from [SavedStateHandle] 
+class DetailInstance(savedState: SavedStateHandle, detail: String) : InstanceKeeper.Instance {
+  private val initialState: DetailState = savedState.get() ?: DetailState(detail)
+  private val stateFlow = MutableStateFlow(initialState)
+  val states: StateFlow<DetailState> = stateFlow
+}
 ```
 
 ## Platform configurations 🚉

decompose-router/api/android/decompose-router.api

@@ -13,6 +13,7 @@ public final class io/github/xxfast/decompose/router/Router : com/arkivanov/deco
 
 public final class io/github/xxfast/decompose/router/RouterKt {
 	public static final fun getLocalRouter ()Landroidx/compose/runtime/ProvidableCompositionLocal;
+	public static final fun rememberOnRoute (Lkotlin/reflect/KClass;Lkotlin/jvm/functions/Function1;Landroidx/compose/runtime/Composer;I)Lcom/arkivanov/essenty/instancekeeper/InstanceKeeper$Instance;
 	public static final fun rememberRouter (Lkotlin/reflect/KClass;Ljava/util/List;ZLandroidx/compose/runtime/Composer;II)Lio/github/xxfast/decompose/router/Router;
 }
 
@@ -48,10 +49,6 @@ public final class io/github/xxfast/decompose/router/SavedStateHandle : com/arki
 	public final fun set (Landroid/os/Parcelable;)V
 }
 
-public final class io/github/xxfast/decompose/router/ViewModelKt {
-	public static final fun rememberViewModel (Lkotlin/reflect/KClass;Lkotlin/jvm/functions/Function1;Landroidx/compose/runtime/Composer;I)Lcom/arkivanov/essenty/instancekeeper/InstanceKeeper$Instance;
-}
-
 public final class io/github/xxfast/decompose/router/content/RoutedContentKt {
 	public static final fun RoutedContent (Lio/github/xxfast/decompose/router/Router;Landroidx/compose/ui/Modifier;Lcom/arkivanov/decompose/extensions/compose/jetbrains/stack/animation/StackAnimation;Lkotlin/jvm/functions/Function3;Landroidx/compose/runtime/Composer;II)V
 }

decompose-router/api/desktop/decompose-router.api

@@ -13,6 +13,7 @@ public final class io/github/xxfast/decompose/router/Router : com/arkivanov/deco
 
 public final class io/github/xxfast/decompose/router/RouterKt {
 	public static final fun getLocalRouter ()Landroidx/compose/runtime/ProvidableCompositionLocal;
+	public static final fun rememberOnRoute (Lkotlin/reflect/KClass;Lkotlin/jvm/functions/Function1;Landroidx/compose/runtime/Composer;I)Lcom/arkivanov/essenty/instancekeeper/InstanceKeeper$Instance;
 	public static final fun rememberRouter (Lkotlin/reflect/KClass;Ljava/util/List;ZLandroidx/compose/runtime/Composer;II)Lio/github/xxfast/decompose/router/Router;
 }
 
@@ -37,10 +38,6 @@ public final class io/github/xxfast/decompose/router/SavedStateHandle : com/arki
 	public final fun set (Lcom/arkivanov/essenty/parcelable/Parcelable;)V
 }
 
-public final class io/github/xxfast/decompose/router/ViewModelKt {
-	public static final fun rememberViewModel (Lkotlin/reflect/KClass;Lkotlin/jvm/functions/Function1;Landroidx/compose/runtime/Composer;I)Lcom/arkivanov/essenty/instancekeeper/InstanceKeeper$Instance;
-}
-
 public final class io/github/xxfast/decompose/router/content/RoutedContentKt {
 	public static final fun RoutedContent (Lio/github/xxfast/decompose/router/Router;Landroidx/compose/ui/Modifier;Lcom/arkivanov/decompose/extensions/compose/jetbrains/stack/animation/StackAnimation;Lkotlin/jvm/functions/Function3;Landroidx/compose/runtime/Composer;II)V
 }

decompose-router/src/androidInstrumentedTest/kotlin/io/github/xxfast/decompose/screen/TestScreens.kt

@@ -46,8 +46,8 @@ import com.arkivanov.decompose.router.stack.pop
 import com.arkivanov.decompose.router.stack.push
 import io.github.xxfast.decompose.router.Router
 import io.github.xxfast.decompose.router.content.RoutedContent
+import io.github.xxfast.decompose.router.rememberOnRoute
 import io.github.xxfast.decompose.router.rememberRouter
-import io.github.xxfast.decompose.router.rememberViewModel
 import io.github.xxfast.decompose.screen.Screen.Round
 
 const val TOOLBAR_TAG = "toolbar"
@@ -82,7 +82,7 @@ fun HomeScreen() {
 fun ListScreen(
   onSelect: (count: Int) -> Unit,
 ) {
-  val instance: ListInstance = rememberViewModel(ListInstance::class) { savedState ->
+  val instance: ListInstance = rememberOnRoute(ListInstance::class) { savedState ->
     ListInstance(savedState)
   }
 

decompose-router/src/commonMain/kotlin/io/github/xxfast/decompose/router/Router.kt

@@ -1,14 +1,21 @@
 package io.github.xxfast.decompose.router
 
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisallowComposableCalls
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.ProvidableCompositionLocal
 import androidx.compose.runtime.State
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.staticCompositionLocalOf
 import com.arkivanov.decompose.ComponentContext
 import com.arkivanov.decompose.router.stack.ChildStack
 import com.arkivanov.decompose.router.stack.StackNavigation
+import com.arkivanov.essenty.instancekeeper.InstanceKeeper
+import com.arkivanov.essenty.instancekeeper.InstanceKeeper.Instance
+import com.arkivanov.essenty.instancekeeper.getOrCreate
 import com.arkivanov.essenty.parcelable.Parcelable
+import com.arkivanov.essenty.statekeeper.StateKeeper
+import io.github.xxfast.decompose.LocalComponentContext
 import io.github.xxfast.decompose.rememberChildStack
 import kotlin.reflect.KClass
 
@@ -58,3 +65,43 @@ fun <C : Parcelable> rememberRouter(
 
   return remember { Router(navigator = navigator, stack = childStackState) }
 }
+
+/***
+ * Creates a instance of [T] that is scoped to the current route
+ *
+ * @param instanceClass class of [T] instance
+ * @param block lambda to create an instance of [T] with a given [SavedStateHandle]
+ */
+@Suppress("UNCHECKED_CAST")
+@Composable
+fun <T : Instance> rememberOnRoute(
+  instanceClass: KClass<T>,
+  block: @DisallowComposableCalls (savedState: SavedStateHandle) -> T
+): T {
+  val component: ComponentContext = LocalComponentContext.current
+  val stateKeeper: StateKeeper = component.stateKeeper
+  val instanceKeeper: InstanceKeeper = component.instanceKeeper
+
+  val packageName: String =
+    requireNotNull(instanceClass.simpleName) { "Unable to retain anonymous instance of $instanceClass"}
+  val instanceKey = "$packageName.instance"
+  val stateKey = "$packageName.savedState"
+
+  val (instance, savedState) = remember(instanceClass) {
+    val savedState: SavedStateHandle = instanceKeeper
+      .getOrCreate(stateKey) { SavedStateHandle(stateKeeper.consume(stateKey, SavedState::class)) }
+    var instance: T? = instanceKeeper.get(instanceKey) as T?
+    if (instance == null) {
+      instance = block(savedState)
+      instanceKeeper.put(instanceKey, instance)
+    }
+    instance to savedState
+  }
+
+  LaunchedEffect(Unit) {
+    if (!stateKeeper.isRegistered(stateKey))
+      stateKeeper.register(stateKey) { savedState.value }
+  }
+
+  return instance
+}