Implement result passing

core/src/main/kotlin/com/kiwi/navigationcompose/typed/ResultDestination.kt

@@ -0,0 +1,25 @@
+package com.kiwi.navigationcompose.typed
+
+/**
+ * Marks the destinations as destination being able to return a result.
+ *
+ * The result type is defined as the generic argument if this interface and has to be KotlinX Serializable.
+ *
+ * Use [ComposableResultEffect] or [DialogResultEffect] to observe the result.
+ * Use [setResult] to send the result from a destination.
+ *
+ * ```
+ * sealed interface Destinations : Destination {
+ *     // ...
+ *     @Serializable
+ * 	   object Dialog : Destinations, ResultDestination<Dialog.Result> {
+ * 	       @Serializable
+ *         data class Result(val name: String)
+ *     }
+ * }
+ * ```
+ *
+ * Opening the same ResultDestination multiple times per screen has to be distinguished by manually sending an
+ * identifier to the result destination and this identifier has to be propagated back by the result type.
+ */
+public interface ResultDestination<T : Any> : Destination

core/src/main/kotlin/com/kiwi/navigationcompose/typed/ResultSharing.kt

@@ -0,0 +1,126 @@
+package com.kiwi.navigationcompose.typed
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleEventObserver
+import androidx.navigation.NavController
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.serializer
+
+/**
+ * Registers an effect for processing a composable destination's result. See [ResultDestination].
+ *
+ * Use only to process a result from "full" destination created by `composable` NavGraph builder function.
+ * If you are expecting a result from dialog or full-screen dialog, [DialogResultEffect] has to be used
+ * to properly handle configuration changes.
+ *
+ * To avoid specifying generic argument types, use type-inference and type the result argument of the block:
+ * ```
+ * ComposableResultEffect(navController) { result: Destinations.Dialog.Result ->
+ *     // handle result
+ * }
+ * ```
+ */
+@Suppress("unused") // T generic parameter is a typecheck for R being the type from ResultDestination
+@ExperimentalSerializationApi
+@Composable
+public inline fun <T : ResultDestination<R>, reified R : Any> ComposableResultEffect(
+	navController: NavController,
+	noinline block: (R) -> Unit,
+) {
+	@Suppress("RemoveExplicitTypeArguments")
+	ResultEffectImpl(
+		navController = navController,
+		currentRoute = navController.currentDestination!!.route!!,
+		resultSerializer = serializer<R>(),
+		block = block,
+	)
+}
+
+/**
+ * Registers an effect for processing a dialog destination's result. See [ResultDestination].
+ *
+ * Use only to process a result from dialog (and full-screen dialog) destination created by `dialog` NavGraph
+ * builder function.
+ *
+ * To avoid specifying generic argument types, use type-inference and type the result argument of the block:
+ * ```
+ * DialogResultEffect(
+ *     currentRoutePattern = createRoutePattern<Destinations.CurrentDestination>(),
+ *     navController = navController,
+ * ) { result: Destinations.Dialog.Result ->
+ * ```
+ */
+@Suppress("unused") // T generic parameter is a typecheck for R being the type from ResultDestination
+@ExperimentalSerializationApi
+@Composable
+public inline fun <T : ResultDestination<R>, reified R : Any> DialogResultEffect(
+	currentRoutePattern: String,
+	navController: NavController,
+	noinline block: (R) -> Unit,
+) {
+	@Suppress("RemoveExplicitTypeArguments")
+	ResultEffectImpl(
+		navController = navController,
+		currentRoute = currentRoutePattern,
+		resultSerializer = serializer<R>(),
+		block = block,
+	)
+}
+
+/**
+ * Implementation of ResultEffect. Use [ComposableResultEffect] or [DialogResultEffect] directly.
+ */
+@ExperimentalSerializationApi
+@Composable
+public fun <R : Any> ResultEffectImpl(
+	navController: NavController,
+	currentRoute: String,
+	resultSerializer: KSerializer<R>,
+	block: (R) -> Unit,
+) {
+	DisposableEffect(navController, block) {
+		// The implementation is based on the official documentation of the Result sharing.
+		// It takes into consideration the possibility of a dialog usage (see the docs).
+		// https://developer.android.com/guide/navigation/navigation-programmatic#additional_considerations
+		val resultKey = resultSerializer.descriptor.serialName + "_result"
+		val backStackEntry = navController.getBackStackEntry(currentRoute)
+		val observer = LifecycleEventObserver { _, event ->
+			if (event == Lifecycle.Event.ON_RESUME && backStackEntry.savedStateHandle.contains(resultKey)) {
+				val result = backStackEntry.savedStateHandle.remove<String>(resultKey)!!
+				val decoded = Json.decodeFromString(resultSerializer, result)
+				block(decoded)
+			}
+		}
+		backStackEntry.lifecycle.addObserver(observer)
+		onDispose {
+			backStackEntry.lifecycle.removeObserver(observer)
+		}
+	}
+}
+
+/**
+ * Sets a destination result for the previous backstack entry's destination.
+ *
+ * The result type has to be KotlinX Serializable.
+ */
+@ExperimentalSerializationApi
+@Suppress("unused") // T generic parameter is a typecheck for R being the type from ResultDestination
+public inline fun <T : ResultDestination<R>, reified R : Any> NavController.setResult(
+	data: R,
+) {
+	setResultImpl(serializer(), data)
+}
+
+@ExperimentalSerializationApi
+public fun <R : Any> NavController.setResultImpl(
+	serializer: KSerializer<R>,
+	data: R,
+) {
+	val result = Json.encodeToString(serializer, data)
+	val resultKey = serializer.descriptor.serialName + "_result"
+	previousBackStackEntry?.savedStateHandle?.set(resultKey, result)
+}

demo/src/main/kotlin/com/kiwi/navigationcompose/typed/demo/Destinations.kt

@@ -1,6 +1,7 @@
 package com.kiwi.navigationcompose.typed.demo
 
 import com.kiwi.navigationcompose.typed.Destination
+import com.kiwi.navigationcompose.typed.ResultDestination
 import kotlinx.serialization.Serializable
 
 internal sealed interface Destinations : Destination {
@@ -30,3 +31,20 @@ internal sealed interface HomeDestinations : Destination {
 		val stringNullableOptional: String? = null,
 	) : HomeDestinations
 }
+
+internal sealed interface ProfileDestinations : Destination {
+	@Serializable
+	object Home : ProfileDestinations
+
+	@Serializable
+	object NameEditDialog : ProfileDestinations, ResultDestination<NameEditDialog.Result> {
+		@Serializable
+		data class Result(val name: String)
+	}
+
+	@Serializable
+	object NameEditScreen : ProfileDestinations, ResultDestination<NameEditScreen.Result> {
+		@Serializable
+		data class Result(val name: String)
+	}
+}

demo/src/main/kotlin/com/kiwi/navigationcompose/typed/demo/NavHost.kt

@@ -8,7 +8,10 @@ import com.kiwi.navigationcompose.typed.createRoutePattern
 import com.kiwi.navigationcompose.typed.demo.screens.Demo
 import com.kiwi.navigationcompose.typed.demo.screens.Home
 import com.kiwi.navigationcompose.typed.demo.screens.List
+import com.kiwi.navigationcompose.typed.demo.screens.NameEditDialog
+import com.kiwi.navigationcompose.typed.demo.screens.NameEditScreen
 import com.kiwi.navigationcompose.typed.demo.screens.Profile
+import com.kiwi.navigationcompose.typed.dialog
 import com.kiwi.navigationcompose.typed.navigate
 import com.kiwi.navigationcompose.typed.navigation
 import kotlinx.serialization.ExperimentalSerializationApi
@@ -27,6 +30,12 @@ internal fun NavHost(navController: NavHostController) {
 			composable<HomeDestinations.Demo> { Demo(this, navController::navigateUp) }
 		}
 		composable<Destinations.List> { List() }
-		composable<Destinations.Profile> { Profile() }
+		navigation<Destinations.Profile>(
+			startDestination = createRoutePattern<ProfileDestinations.Home>(),
+		) {
+			composable<ProfileDestinations.Home> { Profile(navController) }
+			dialog<ProfileDestinations.NameEditDialog> { NameEditDialog(navController) }
+			composable<ProfileDestinations.NameEditScreen> { NameEditScreen(navController) }
+		}
 	}
 }

demo/src/main/kotlin/com/kiwi/navigationcompose/typed/demo/screens/NameEditDialog.kt

@@ -0,0 +1,50 @@
+package com.kiwi.navigationcompose.typed.demo.screens
+
+import androidx.compose.material.AlertDialog
+import androidx.compose.material.OutlinedTextField
+import androidx.compose.material.Text
+import androidx.compose.material.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.navigation.NavController
+import com.kiwi.navigationcompose.typed.demo.ProfileDestinations
+import com.kiwi.navigationcompose.typed.setResult
+import kotlinx.serialization.ExperimentalSerializationApi
+
+@ExperimentalSerializationApi
+@Composable
+internal fun NameEditDialog(navController: NavController) {
+	NameEdit(
+		onNameSave = { name ->
+			navController.setResult(ProfileDestinations.NameEditDialog.Result(name))
+			navController.navigateUp()
+		},
+		onDismiss = navController::navigateUp,
+	)
+}
+
+@Composable
+private fun NameEdit(
+	onNameSave: (String) -> Unit,
+	onDismiss: () -> Unit,
+) {
+	var name by rememberSaveable { mutableStateOf("") }
+	AlertDialog(
+		onDismissRequest = onDismiss,
+		title = { Text("Set your name") },
+		text = {
+			OutlinedTextField(
+				value = name,
+				onValueChange = { name = it },
+			)
+		},
+		confirmButton = {
+			TextButton(onClick = { onNameSave(name) }) {
+				Text("Save")
+			}
+		},
+	)
+}

demo/src/main/kotlin/com/kiwi/navigationcompose/typed/demo/screens/NameEditScreen.kt

@@ -0,0 +1,43 @@
+package com.kiwi.navigationcompose.typed.demo.screens
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.material.OutlinedTextField
+import androidx.compose.material.Text
+import androidx.compose.material.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.navigation.NavController
+import com.kiwi.navigationcompose.typed.demo.ProfileDestinations
+import com.kiwi.navigationcompose.typed.setResult
+import kotlinx.serialization.ExperimentalSerializationApi
+
+@ExperimentalSerializationApi
+@Composable
+internal fun NameEditScreen(navController: NavController) {
+	NameEdit(
+		onNameSave = { name ->
+			navController.setResult(ProfileDestinations.NameEditScreen.Result(name))
+			navController.navigateUp()
+		},
+	)
+}
+
+@Composable
+private fun NameEdit(
+	onNameSave: (String) -> Unit,
+) {
+	var name by rememberSaveable { mutableStateOf("") }
+	Column {
+		Text("Set your name")
+		OutlinedTextField(
+			value = name,
+			onValueChange = { name = it },
+		)
+		TextButton(onClick = { onNameSave(name) }) {
+			Text("Save")
+		}
+	}
+}

demo/src/main/kotlin/com/kiwi/navigationcompose/typed/demo/screens/Profile.kt

@@ -1,9 +1,72 @@
 package com.kiwi.navigationcompose.typed.demo.screens
 
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.wrapContentSize
+import androidx.compose.material.OutlinedButton
 import androidx.compose.material.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.navigation.NavController
+import com.kiwi.navigationcompose.typed.ComposableResultEffect
+import com.kiwi.navigationcompose.typed.Destination
+import com.kiwi.navigationcompose.typed.DialogResultEffect
+import com.kiwi.navigationcompose.typed.createRoutePattern
+import com.kiwi.navigationcompose.typed.demo.ProfileDestinations
+import com.kiwi.navigationcompose.typed.navigate
+import kotlinx.serialization.ExperimentalSerializationApi
 
+@ExperimentalSerializationApi
 @Composable
-internal fun Profile() {
-	Text("Profile")
+internal fun Profile(navController: NavController) {
+	var name by rememberSaveable { mutableStateOf("") }
+	var times by rememberSaveable { mutableStateOf(0) }
+
+	DialogResultEffect(
+		currentRoutePattern = createRoutePattern<ProfileDestinations.Home>(),
+		navController = navController,
+	) { result: ProfileDestinations.NameEditDialog.Result ->
+		name = "Dialog: ${result.name}"
+		times += 1
+	}
+	ComposableResultEffect(navController) { result: ProfileDestinations.NameEditScreen.Result ->
+		name = "Screen: ${result.name}"
+		times += 1
+	}
+
+	Profile(name, times, navController::navigate)
+}
+
+@Composable
+private fun Profile(
+	name: String,
+	times: Int,
+	onNavigate: (Destination) -> Unit,
+) {
+	Column(
+		Modifier
+			.fillMaxSize()
+			.wrapContentSize(),
+		horizontalAlignment = Alignment.CenterHorizontally,
+	) {
+		Text("Profile")
+
+		Text("Name: $name, changed: $times")
+
+		OutlinedButton(
+			onClick = { onNavigate(ProfileDestinations.NameEditDialog) },
+		) {
+			Text("Change Name Dialog")
+		}
+		OutlinedButton(
+			onClick = { onNavigate(ProfileDestinations.NameEditScreen) },
+		) {
+			Text("Change Name Screen")
+		}
+	}
 }