Merge pull request #143 from arkivanov/fix-LifecycleRegistry-callback-order-when-shutting-down

Fix LifecycleRegistry callback order when shutting down

Author: arkivanov

mvikotlin/src/commonMain/kotlin/com/arkivanov/mvikotlin/core/lifecycle/LifecycleRegistry.kt

@@ -55,16 +55,16 @@ class LifecycleRegistry : Lifecycle, Lifecycle.Callbacks {
 
     override fun onPause() {
         setState(required = Lifecycle.State.RESUMED, newState = Lifecycle.State.STARTED)
-        set.forEach(Lifecycle.Callbacks::onPause)
+        set.reversed().forEach(Lifecycle.Callbacks::onPause)
     }
 
     override fun onStop() {
-        set.forEach(Lifecycle.Callbacks::onStop)
+        set.reversed().forEach(Lifecycle.Callbacks::onStop)
         setState(required = Lifecycle.State.STARTED, newState = Lifecycle.State.CREATED)
     }
 
     override fun onDestroy() {
-        set.forEach(Lifecycle.Callbacks::onDestroy)
+        set.reversed().forEach(Lifecycle.Callbacks::onDestroy)
         set = emptySet()
         setState(required = Lifecycle.State.CREATED, newState = Lifecycle.State.DESTROYED)
     }

mvikotlin/src/commonTest/kotlin/com/arkivanov/mvikotlin/core/lifecycle/LifecycleRegistryTest.kt

@@ -7,6 +7,7 @@ import com.arkivanov.mvikotlin.core.lifecycle.TestLifecycleCallbacks.Event.ON_RE
 import com.arkivanov.mvikotlin.core.lifecycle.TestLifecycleCallbacks.Event.ON_START
 import com.arkivanov.mvikotlin.core.lifecycle.TestLifecycleCallbacks.Event.ON_STOP
 import kotlin.test.Test
+import kotlin.test.assertEquals
 
 class LifecycleRegistryTest {
 
@@ -34,6 +35,40 @@ class LifecycleRegistryTest {
         callbacks2.assertEvents(events)
     }
 
+    @Test
+    fun calls_all_callbacks_in_proper_order() {
+        val events = ArrayList<String>()
+        val callbacks1 = TestLifecycleCallbacks { events += "first-$it" }
+        val callbacks2 = TestLifecycleCallbacks { events += "second-$it" }
+
+        lifecycle.subscribe(callbacks1)
+        lifecycle.subscribe(callbacks2)
+        lifecycle.onCreate()
+        lifecycle.onStart()
+        lifecycle.onResume()
+        lifecycle.onPause()
+        lifecycle.onStop()
+        lifecycle.onDestroy()
+
+        assertEquals(
+            listOf(
+                "first-$ON_CREATE",
+                "second-$ON_CREATE",
+                "first-$ON_START",
+                "second-$ON_START",
+                "first-$ON_RESUME",
+                "second-$ON_RESUME",
+                "second-$ON_PAUSE",
+                "first-$ON_PAUSE",
+                "second-$ON_STOP",
+                "first-$ON_STOP",
+                "second-$ON_DESTROY",
+                "first-$ON_DESTROY"
+            ),
+            events
+        )
+    }
+
     @Test
     fun drives_callback_to_created_state_WHEN_created_and_subscribed() {
         lifecycle.onCreate()

mvikotlin/src/commonTest/kotlin/com/arkivanov/mvikotlin/core/lifecycle/TestCallbacks.kt

@@ -2,32 +2,39 @@ package com.arkivanov.mvikotlin.core.lifecycle
 
 import kotlin.test.assertEquals
 
-class TestLifecycleCallbacks : Lifecycle.Callbacks {
+class TestLifecycleCallbacks(
+    private val onEvent: (Event) -> Unit = {}
+) : Lifecycle.Callbacks {
 
     private val events = ArrayList<Event>()
 
     override fun onCreate() {
-        events += Event.ON_CREATE
+        onEvent(Event.ON_CREATE)
     }
 
     override fun onStart() {
-        events += Event.ON_START
+        onEvent(Event.ON_START)
     }
 
     override fun onResume() {
-        events += Event.ON_RESUME
+        onEvent(Event.ON_RESUME)
     }
 
     override fun onPause() {
-        events += Event.ON_PAUSE
+        onEvent(Event.ON_PAUSE)
     }
 
     override fun onStop() {
-        events += Event.ON_STOP
+        onEvent(Event.ON_STOP)
     }
 
     override fun onDestroy() {
-        events += Event.ON_DESTROY
+        onEvent(Event.ON_DESTROY)
+    }
+
+    private fun onEvent(event: Event) {
+        events += event
+        onEvent.invoke(event)
     }
 
     fun assertEvents(events: List<Event>) {