vault backup: 2024-10-12 17:19:45

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Blueprint/HasDedicatedAsyncNode/HasDedicatedAsyncNode.md

@@ -0,0 +1,172 @@
+# HasDedicatedAsyncNode
+
+- **使用位置：** UCLASS
+- **元数据类型：** bool
+- **关联项：** [ExposedAsyncProxy](../ExposedAsyncProxy/ExposedAsyncProxy.md)
+
+隐藏UBlueprintAsyncActionBase子类里工厂方法自动生成的蓝图异步节点，以便自己可以手动自定义创建一个相应的UK2Node_XXX。
+
+```cpp
+/**
+* BlueprintCallable factory functions for classes which inherit from UBlueprintAsyncActionBase will have a special blueprint node created for it: UK2Node_AsyncAction
+* You can stop this node spawning and create a more specific one by adding the UCLASS metadata "HasDedicatedAsyncNode"
+*/
+
+UCLASS(MinimalAPI)
+class UBlueprintAsyncActionBase : public UObject
+{}
+```
+
+## 测试代码：
+
+```cpp
+UCLASS(Blueprintable, BlueprintType,meta = (ExposedAsyncProxy = MyAsyncObject,HasDedicatedAsyncNode))
+class INSIDER_API UMyFunction_Async :public UCancellableAsyncAction
+{}
+
+//可以自定义一个K2Node
+UCLASS()
+class INSIDER_API UK2Node_MyFunctionAsyncAction : public UK2Node_AsyncAction
+{
+	GENERATED_BODY()
+
+	// UK2Node interface
+	virtual void GetMenuActions(FBlueprintActionDatabaseRegistrar& ActionRegistrar) const override;
+	virtual void AllocateDefaultPins() override;
+	// End of UK2Node interface
+
+protected:
+	virtual bool HandleDelegates(
+		const TArray<FBaseAsyncTaskHelper::FOutputPinAndLocalVariable>& VariableOutputs, UEdGraphPin* ProxyObjectPin,
+		UEdGraphPin*& InOutLastThenPin, UEdGraph* SourceGraph, FKismetCompilerContext& CompilerContext) override;
+};
+
+void UK2Node_MyFunctionAsyncAction::GetMenuActions(FBlueprintActionDatabaseRegistrar& ActionRegistrar) const
+{
+	struct GetMenuActions_Utils
+	{
+		static void SetNodeFunc(UEdGraphNode* NewNode, bool /*bIsTemplateNode*/, TWeakObjectPtr<UFunction> FunctionPtr)
+		{
+			UK2Node_MyFunctionAsyncAction* AsyncTaskNode = CastChecked<UK2Node_MyFunctionAsyncAction>(NewNode);
+			if (FunctionPtr.IsValid())
+			{
+				UFunction* Func = FunctionPtr.Get();
+				FObjectProperty* ReturnProp = CastFieldChecked<FObjectProperty>(Func->GetReturnProperty());
+
+				AsyncTaskNode->ProxyFactoryFunctionName = Func->GetFName();
+				AsyncTaskNode->ProxyFactoryClass = Func->GetOuterUClass();
+				AsyncTaskNode->ProxyClass = ReturnProp->PropertyClass;
+				AsyncTaskNode->NodeComment = TEXT("This is MyCustomK2Node");
+			}
+		}
+	};
+
+	UClass* NodeClass = GetClass();
+	ActionRegistrar.RegisterClassFactoryActions<UMyFunction_Async>(FBlueprintActionDatabaseRegistrar::FMakeFuncSpawnerDelegate::CreateLambda([NodeClass](const UFunction* FactoryFunc)->UBlueprintNodeSpawner*
+		{
+			UBlueprintNodeSpawner* NodeSpawner = UBlueprintFunctionNodeSpawner::Create(FactoryFunc);
+			check(NodeSpawner != nullptr);
+			NodeSpawner->NodeClass = NodeClass;
+
+			TWeakObjectPtr<UFunction> FunctionPtr = MakeWeakObjectPtr(const_cast<UFunction*>(FactoryFunc));
+			NodeSpawner->CustomizeNodeDelegate = UBlueprintNodeSpawner::FCustomizeNodeDelegate::CreateStatic(GetMenuActions_Utils::SetNodeFunc, FunctionPtr);
+
+			return NodeSpawner;
+		}));
+}
+
+void UK2Node_MyFunctionAsyncAction::AllocateDefaultPins()
+{
+	Super::AllocateDefaultPins();
+}
+
+bool UK2Node_MyFunctionAsyncAction::HandleDelegates(const TArray<FBaseAsyncTaskHelper::FOutputPinAndLocalVariable>& VariableOutputs, UEdGraphPin* ProxyObjectPin, UEdGraphPin*& InOutLastThenPin, UEdGraph* SourceGraph, FKismetCompilerContext& CompilerContext)
+{
+	bool bIsErrorFree = true;
+
+	for (TFieldIterator<FMulticastDelegateProperty> PropertyIt(ProxyClass); PropertyIt && bIsErrorFree; ++PropertyIt)
+	{
+		UEdGraphPin* LastActivatedThenPin = nullptr;
+		bIsErrorFree &= FBaseAsyncTaskHelper::HandleDelegateImplementation(*PropertyIt, VariableOutputs, ProxyObjectPin, InOutLastThenPin, LastActivatedThenPin, this, SourceGraph, CompilerContext);
+	}
+
+	return bIsErrorFree;
+}
+
+```
+
+## 蓝图效果：
+
+左侧是引擎自带的UK2Node_AsyncAction生成节点，右边是自定义的UK2Node_MyFunctionAsyncAction生成的蓝图节点，虽然功能一致，但是右边额外加了个注释以便区分。有了这个基础，你也可以在其中继续重载方法进一步自定义。
+
+![Untitled](Untitled.png)
+
+## 当前在源码里有两处地方使用：
+
+```cpp
+UCLASS(BlueprintType, meta = (ExposedAsyncProxy = "AsyncTask", HasDedicatedAsyncNode))
+class GAMEPLAYMESSAGES_API UAsyncAction_RegisterGameplayMessageReceiver : public UBlueprintAsyncActionBase
+{
+	UFUNCTION(BlueprintCallable, Category = Messaging, meta=(WorldContext="WorldContextObject", BlueprintInternalUseOnly="true"))
+	static UAsyncAction_RegisterGameplayMessageReceiver* RegisterGameplayMessageReceiver(UObject* WorldContextObject, FEventMessageTag Channel, UScriptStruct* PayloadType, EGameplayMessageMatchType MatchType = EGameplayMessageMatchType::ExactMatch, AActor* ActorContext = nullptr);
+
+}
+//由UK2Node_GameplayMessageAsyncAction来负责创建
+void UK2Node_GameplayMessageAsyncAction::GetMenuActions(FBlueprintActionDatabaseRegistrar& ActionRegistrar) const
+{
+	//...
+	UClass* NodeClass = GetClass();
+	ActionRegistrar.RegisterClassFactoryActions<UAsyncAction_RegisterGameplayMessageReceiver>(FBlueprintActionDatabaseRegistrar::FMakeFuncSpawnerDelegate::CreateLambda([NodeClass](const UFunction* FactoryFunc)->UBlueprintNodeSpawner*
+	{
+		UBlueprintNodeSpawner* NodeSpawner = UBlueprintFunctionNodeSpawner::Create(FactoryFunc);
+		check(NodeSpawner != nullptr);
+		NodeSpawner->NodeClass = NodeClass;
+
+		TWeakObjectPtr<UFunction> FunctionPtr = MakeWeakObjectPtr(const_cast<UFunction*>(FactoryFunc));
+		NodeSpawner->CustomizeNodeDelegate = UBlueprintNodeSpawner::FCustomizeNodeDelegate::CreateStatic(GetMenuActions_Utils::SetNodeFunc, FunctionPtr);
+
+		return NodeSpawner;
+	}) );
+}
+
+UCLASS(BlueprintType, meta=(ExposedAsyncProxy = "AsyncTask", HasDedicatedAsyncNode))
+class UMovieSceneAsyncAction_SequencePrediction : public UBlueprintAsyncActionBase
+{
+	UFUNCTION(BlueprintCallable, Category=Cinematics)
+	static UMovieSceneAsyncAction_SequencePrediction* PredictWorldTransformAtTime(UMovieSceneSequencePlayer* Player, USceneComponent* TargetComponent, float TimeInSeconds);
+}
+```
+
+## 生成的蓝图：
+
+UAsyncAction_RegisterGameplayMessageReceiver由自定义的UK2Node_GameplayMessageAsyncAction来创建蓝图节点，从而提供了一个泛型的Payload输出引脚。而UMovieSceneAsyncAction_SequencePrediction 里的工厂方法PredictWorldTransformAtTime，由于隐藏了自动生成的版本，又没有加上BlueprintInternalUseOnly来抑制UHT生成的版本，因此最终呈现的是普通版本的静态函数蓝图节点。
+
+![Untitled](Untitled%201.png)
+
+## 源码里的作用机制：
+
+可以看到，如果在类上有找到HasDedicatedAsyncNode，直接就返回nullptr，不再生成NodeSpawner，因此就阻止了蓝图节点的生成。
+
+```cpp
+void UK2Node_AsyncAction::GetMenuActions(FBlueprintActionDatabaseRegistrar& ActionRegistrar) const
+{
+	ActionRegistrar.RegisterClassFactoryActions<UBlueprintAsyncActionBase>(FBlueprintActionDatabaseRegistrar::FMakeFuncSpawnerDelegate::CreateLambda([NodeClass](const UFunction* FactoryFunc)->UBlueprintNodeSpawner*
+	{
+		UClass* FactoryClass = FactoryFunc ? FactoryFunc->GetOwnerClass() : nullptr;
+		if (FactoryClass && FactoryClass->HasMetaData(TEXT("HasDedicatedAsyncNode")))
+		{
+			// Wants to use a more specific blueprint node to handle the async action
+			return nullptr;
+		}
+	
+		UBlueprintNodeSpawner* NodeSpawner = UBlueprintFunctionNodeSpawner::Create(FactoryFunc);
+		check(NodeSpawner != nullptr);
+		NodeSpawner->NodeClass = NodeClass;
+	
+		TWeakObjectPtr<UFunction> FunctionPtr = MakeWeakObjectPtr(const_cast<UFunction*>(FactoryFunc));
+		NodeSpawner->CustomizeNodeDelegate = UBlueprintNodeSpawner::FCustomizeNodeDelegate::CreateStatic(GetMenuActions_Utils::SetNodeFunc, FunctionPtr);
+	
+		return NodeSpawner;
+	}) );
+}
+```