101 lines
3.4 KiB
Markdown
101 lines
3.4 KiB
Markdown
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# HasNativeBreak
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- **功能描述：** 为该结构指定一个C++内的UFunction函数作为Break节点的实现
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- **使用位置：** USTRUCT
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- **引擎模块：** Struct
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- **元数据类型：** string="abc"
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- **关联项：** [HasNativeMake](../HasNativeMake.md)
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- **常用程度：** ★★★★★
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为该结构指定一个C++内的UFunction函数作为Break节点的实现
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指定一个static *UFunction函数的完整路径值，一般是”/*Script/*Module.Class.Function”*
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这个函数一般是BlueprintThreadSafe，因为这种纯Make和Break函数一般不带副作用，因此可以随便的多线程调用。
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## 测试代码：
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```cpp
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//(BlueprintType = true, HasNativeBreak = /Script/Insider.MyHasNativeStructHelperLibrary.BreakMyHasNativeStruct, HasNativeMake = /Script/Insider.MyHasNativeStructHelperLibrary.MakeMyHasNativeStruct, ModuleRelativePath = Struct/MyStruct_NativeMakeBreak.h)
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USTRUCT(BlueprintType, meta = (HasNativeBreak = "/Script/Insider.MyHasNativeStructHelperLibrary.BreakMyHasNativeStruct", HasNativeMake = "/Script/Insider.MyHasNativeStructHelperLibrary.MakeMyHasNativeStruct"))
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struct INSIDER_API FMyStruct_HasNative
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{
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GENERATED_BODY()
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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float MyReadWrite;
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UPROPERTY(BlueprintReadOnly, EditAnywhere)
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float MyReadOnly;
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UPROPERTY(EditAnywhere)
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float MyNotBlueprint;
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};
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USTRUCT(BlueprintType)
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struct INSIDER_API FMyStruct_HasDefaultMakeBreak
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{
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GENERATED_BODY()
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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float MyReadWrite;
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UPROPERTY(BlueprintReadOnly, EditAnywhere)
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float MyReadOnly;
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UPROPERTY(EditAnywhere)
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float MyNotBlueprint;
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};
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UCLASS()
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class UMyHasNativeStructHelperLibrary : public UBlueprintFunctionLibrary
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{
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GENERATED_BODY()
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public:
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UFUNCTION(BlueprintPure, meta = (BlueprintThreadSafe))
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static void BreakMyHasNativeStruct(const FMyStruct_HasNative& myStruct, float& outValue)
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{
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outValue = myStruct.MyReadWrite + myStruct.MyReadOnly + myStruct.MyNotBlueprint;
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}
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UFUNCTION(BlueprintPure, meta = (BlueprintThreadSafe))
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static FMyStruct_HasNative MakeMyHasNativeStruct(float value)
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{
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FMyStruct_HasNative result;
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result.MyReadWrite = value;
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result.MyReadOnly = value;
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result.MyNotBlueprint = value;
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return result;
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}
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};
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```
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## 蓝图节点：
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## 原理是：
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通过Meta里配置的值去找UFunction函数，因此我们配置的时候需要提供的是能找到UFunction的完整路径值。这个函数的签名会自动的被反射提取信息到UK2Node_CallFunction节点上，从而构造出不同样式的Make和Break蓝图节点。
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```cpp
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E:\P4V\Engine\Source\Editor\BlueprintGraph\Private\EdGraphSchema_K2.cpp
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const FString& MetaData = StructType->GetMetaData(FBlueprintMetadata::MD_NativeMakeFunction);
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const UFunction* Function = FindObject<UFunction>(nullptr, *MetaData, true);
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UK2Node_CallFunction* CallFunctionNode;
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if (Params.bTransient || Params.CompilerContext)
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{
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CallFunctionNode = (Params.bTransient ? NewObject<UK2Node_CallFunction>(Graph) : Params.CompilerContext->SpawnIntermediateNode<UK2Node_CallFunction>(GraphNode, Params.SourceGraph));
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CallFunctionNode->SetFromFunction(Function);
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CallFunctionNode->AllocateDefaultPins();
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}
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else
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{
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FGraphNodeCreator<UK2Node_CallFunction> MakeStructCreator(*Graph);
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CallFunctionNode = MakeStructCreator.CreateNode(false);
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CallFunctionNode->SetFromFunction(Function);
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MakeStructCreator.Finalize();
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}
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SplitPinNode = CallFunctionNode;
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```
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