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

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+# SetParam
+
+- **功能描述：** 指定一个函数为使用Set<TItem>的函数，元素类型为通配符的泛型。
+- **使用位置：** UFUNCTION
+- **引擎模块：** Blueprint
+- **元数据类型：** string="A | B | C"
+- **限制类型：** TSet
+- **常用程度：** ★★★
+
+源码在UBlueprintSetLibrary。
+
+SetParam支持多个Set和元素参数，以‘,’分隔开，然后Pin的引脚可以通过‘|’继续分隔，形成”SetA | ItemA, SetB | ItemB”的多组数据。
+
+## 测试代码：
+
+```cpp
+	UFUNCTION(BlueprintCallable, CustomThunk, meta = (SetParam = "SetA|ItemA,SetB|ItemB"))
+	static void MySet_Add2(const TSet<int32>& SetA, const int32& ItemA, const TSet<int32>& SetB, const int32& ItemB);
+	static void GenericMySet_Add2(const void* TargetSet, const FSetProperty* SetA, const void* ItemA, const FSetProperty* SetB, const void* ItemB);
+	DECLARE_FUNCTION(execMySet_Add2);
+```
+
+## 蓝图里效果：
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+用‘,’分隔的是组，组内用’|’分隔的参数Pin都是同一种类型的。
+
+```cpp
+void UK2Node_CallFunction::ConformContainerPins()
+{
+		// find any pins marked as SetParam
+		const FString& SetPinMetaData = TargetFunction->GetMetaData(FBlueprintMetadata::MD_SetParam);
+		
+		// useless copies/allocates in this code, could be an optimization target...
+		TArray<FString> SetParamPinGroups;
+		{
+			SetPinMetaData.ParseIntoArray(SetParamPinGroups, TEXT(","), true);
+		}
+		
+		for (FString& Entry : SetParamPinGroups)
+		{
+			// split the group:
+			TArray<FString> GroupEntries;
+			Entry.ParseIntoArray(GroupEntries, TEXT("|"), true);
+			// resolve pins
+			TArray<UEdGraphPin*> ResolvedPins;
+			for(UEdGraphPin* Pin : Pins)
+			{
+				if (GroupEntries.Contains(Pin->GetName()))
+				{
+					ResolvedPins.Add(Pin);
+				}
+			}
+		
+			// if nothing is connected (or non-default), reset to wildcard
+			// else, find the first type and propagate to everyone else::
+			bool bReadyToPropagatSetType = false;
+			FEdGraphTerminalType TypeToPropagate;
+			for (UEdGraphPin* Pin : ResolvedPins)
+			{
+				TryReadTypeToPropagate(Pin, bReadyToPropagatSetType, TypeToPropagate);
+				if(bReadyToPropagatSetType)
+				{
+					break;
+				}
+			}
+		
+			for (UEdGraphPin* Pin : ResolvedPins)
+			{
+				TryPropagateType( Pin, TypeToPropagate, bReadyToPropagatSetType );
+			}
+		}
+	}
+```