Merge pull request #92 from kiwicom/result-processing

Fix NPE in result processing

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

@@ -2,9 +2,14 @@ package com.kiwi.navigationcompose.typed
 
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
 import androidx.navigation.NavController
+import kotlinx.coroutines.flow.filterNotNull
+import kotlinx.coroutines.flow.first
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.json.Json
@@ -31,9 +36,23 @@ public inline fun <reified T : ResultDestination<R>, reified R : Any> Composable
 	navController: NavController,
 	noinline block: (R) -> Unit,
 ) {
+	// The async waiting workarounds situations when navController.currentBackStackEntry is null
+	// ~ not yet populated.
+	val currentDestinationState = remember(navController) {
+		mutableStateOf(navController.currentDestination)
+	}
+	val currentDestination = currentDestinationState.value
+	if (currentDestination == null) {
+		LaunchedEffect(navController) {
+			val currentBackStackEntry = navController.currentBackStackEntryFlow.filterNotNull().first()
+			currentDestinationState.value = currentBackStackEntry.destination
+		}
+		return
+	}
+
 	ResultEffectImpl(
 		navController = navController,
-		currentRoute = navController.currentDestination!!.route!!,
+		currentRoute = currentDestination.route!!, // routes are always not null in Nav Compose
 		destinationSerializer = serializer<T>(),
 		resultSerializer = serializer<R>(),
 		block = block,

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

@@ -20,9 +20,9 @@ internal fun NameEditDialog(navController: NavController) {
 	NameEdit(
 		onNameSave = { name ->
 			navController.setResult(ProfileDestinations.NameEditDialog.Result(name))
-			navController.navigateUp()
+			navController.popBackStack()
 		},
-		onDismiss = navController::navigateUp,
+		onDismiss = navController::popBackStack,
 	)
 }
 

readme.md

@@ -150,7 +150,9 @@ Another set of functionality is provided to support the result sharing. First, d
 
 ```kotlin
 import com.kiwi.navigationcompose.typed.Destination
+import com.kiwi.navigationcompose.typed.DialogResultEffect
 import com.kiwi.navigationcompose.typed.ResultDestination
+import com.kiwi.navigationcompose.typed.setResult
 
 sealed interface Destinations : Destination {
 	@Serializable
@@ -164,7 +166,7 @@ sealed interface Destinations : Destination {
 
 @Composable
 fun Host(navController: NavController) {
-	ComposableResultEffect(navController) { result: Destinations.Dialog.Result ->
+	DialogResultEffect(navController) { result: Destinations.Dialog.Result ->
 		println(result)
 		// process the result
 	}
@@ -175,4 +177,16 @@ fun Host(navController: NavController) {
 		Text("Open")
 	}
 }
+
+@Composable
+fun Dialog(navController: NavController) {
+	Button(
+		onClick = {
+			navController.setResult(Destinations.Dialog.Result(something = 42))
+			navController.popBackStack()
+		}
+	) {
+		Text("Set and close")
+	}
+}
 ```