[fix] Fix setting of DataState::lastData field from FinishedEvent

Add sample of using FinishedEvent along with DataState.

Author: nsk90

README.md

@@ -109,6 +109,7 @@ fun main() {
   </p>
 
 * [Transition on FinishedEvent sample](./samples/src/main/kotlin/ru/nsk/samples/FinishedEventSample.kt)
+* [FinishedEvent using with DataState sample](./samples/src/main/kotlin/ru/nsk/samples/FinishedEventDataStateSample.kt)
 * [Undo transition sample](./samples/src/main/kotlin/ru/nsk/samples/UndoTransitionSample.kt)
 * [PlantUML nested states export sample](./samples/src/main/kotlin/ru/nsk/samples/PlantUmlExportSample.kt)
 * [Inherit transitions by grouping states sample](./samples/src/main/kotlin/ru/nsk/samples/InheritTransitionsSample.kt)

kstatemachine/src/main/kotlin/ru/nsk/kstatemachine/DefaultDataState.kt

@@ -26,19 +26,28 @@ open class DefaultDataState<D : Any>(
         }
 
     override fun onDoEnter(transitionParams: TransitionParams<*>) {
+        fun assign(data: D?) {
+            if (data != null) {
+                _data = data
+                _lastData = data
+            } else {
+                _data = lastData
+            }
+        }
+
         if (this == transitionParams.direction.targetState) {
             when (val event = transitionParams.event) {
-                is DataEvent<*> -> assignEvent(event)
-                is WrappedEvent -> assignEvent(event.event)
-                is FinishedEvent -> _data = dataExtractor.extractFinishedEvent(transitionParams, event) ?: lastData
-                else -> _data = dataExtractor.extract(transitionParams) ?: lastData
+                is DataEvent<*> -> assignData(event)
+                is WrappedEvent -> assignData(event.event)
+                is FinishedEvent -> assign(dataExtractor.extractFinishedEvent(transitionParams, event))
+                else -> assign(dataExtractor.extract(transitionParams))
             }
         } else { // implicit activation
             _data = lastData
         }
     }
 
-    private fun assignEvent(event: Event) {
+    private fun assignData(event: Event) {
         @Suppress("UNCHECKED_CAST")
         event as DataEvent<D>
         with(event.data) {

kstatemachine/src/main/kotlin/ru/nsk/kstatemachine/PendingEventHandler.kt

@@ -24,7 +24,7 @@ private class QueuePendingEventHandlerImpl(private val machine: StateMachine) :
     override fun checkEmpty() = check(queue.isEmpty()) { "Event queue is not empty, internal error" }
 
     override fun onPendingEvent(pendingEvent: Event, argument: Any?) {
-        machine.log { "$machine queued event $pendingEvent with argument $argument " }
+        machine.log { "$machine queued event ${pendingEvent::class.simpleName} with argument $argument" }
         queue.add(EventAndArgument(pendingEvent, argument))
     }
 

kstatemachine/src/test/kotlin/ru/nsk/kstatemachine/TypesafeTransitionTest.kt

@@ -272,6 +272,7 @@ class TypesafeTransitionTest : StringSpec({
             dataState = dataState(defaultData = 42)
         }
         dataState.data shouldBe 0
+        dataState.lastData shouldBe 0
     }
 
     "targeting DataState by conditionalTransition() with custom extractor" {
@@ -294,6 +295,7 @@ class TypesafeTransitionTest : StringSpec({
         }
         machine.processEvent(CustomDataEvent(42))
         dataState.data shouldBe 42
+        dataState.lastData shouldBe 42
     }
 }) {
     class CustomDataEvent(val value: Int) : Event

samples/src/main/kotlin/ru/nsk/samples/FinishedEventDataStateSample.kt

@@ -0,0 +1,48 @@
+package ru.nsk.samples
+
+import ru.nsk.kstatemachine.*
+import ru.nsk.samples.FinishedEventDataStateSample.IntEvent
+import ru.nsk.samples.FinishedEventDataStateSample.States.*
+
+private object FinishedEventDataStateSample {
+    data class IntEvent(override val data: Int) : DataEvent<Int>
+
+    sealed interface States {
+        object State1 : States, DefaultState()
+        object State2 : States, DefaultFinalDataState<Int>(dataExtractor = defaultDataExtractor())
+        object State11 : States, DefaultState()
+        object State12 : States, DefaultFinalDataState<Int>(dataExtractor = defaultDataExtractor())
+    }
+}
+
+private const val DATA = 42
+
+/**
+ * [FinishedEvent] is generated when state enters its child final state.
+ * If final state is [DataState] the event will receive its data field value.
+ * This data may be passed to another [DataState]
+ */
+fun main() {
+    val machine = createStateMachine {
+        logger = StateMachine.Logger { println(it) }
+
+        addInitialState(State1) {
+            addInitialState(State11) {
+                dataTransition<IntEvent, Int>(targetState = State12)
+            }
+            // State1 finished when reaches its child final state
+            addFinalState(State12)
+            // FinishedEvent containing data value from FinalState is generated by the library when State1 finishes
+            transitionConditionally<FinishedEvent> {
+                direction = { targetState(State2) }
+                onTriggered { check(it.event.data == DATA) }
+            }
+        }
+        addState(State2)
+    }
+
+    machine.processEvent(IntEvent(DATA))
+
+    check(State2 in machine.activeStates())
+    check(State2.lastData == DATA)
+}

samples/src/main/kotlin/ru/nsk/samples/FinishedEventSample.kt

@@ -16,7 +16,7 @@ private object FinishedEventSample {
 }
 
 /**
- * FinishedEvent is generated when state enters its child final state
+ * [FinishedEvent] is generated when state enters its child final state
  */
 fun main() {
     val machine = createStateMachine {