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

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+# RestrictedToClasses
+
+- **功能描述：** 限制蓝图函数库下的函数只能在RestrictedToClasses指定的类蓝图中右键创建出来
+- **使用位置：** UCLASS
+- **引擎模块：** Blueprint
+- **元数据类型：** strings="a，b，c"
+- **限制类型：** BlueprintFunctionLibrary
+- **常用程度：** ★★★
+
+在蓝图函数库上使用，指定该函数库中的函数只能用在RestrictedToClasses指定的类的蓝图中，不能在别的蓝图类中被右键出来。
+
+## 测试代码：
+
+```cpp
+UCLASS(Blueprintable)
+class INSIDER_API UMyClass_RestrictedToClasses :public UObject
+{
+	GENERATED_BODY()
+public:
+	UPROPERTY(BlueprintReadWrite,EditAnywhere)
+	float MyFloat;
+};
+
+UCLASS(meta=(RestrictedToClasses="MyClass_RestrictedToClasses"))
+class INSIDER_API UMyClass_RestrictedToClassesLibrary : public UBlueprintFunctionLibrary
+{
+	GENERATED_BODY()
+public:
+	UFUNCTION(BlueprintCallable)
+	static float GetMyClassRestrictedFloat(UMyClass_RestrictedToClasses* myObject) {return myObject->MyFloat;}
+};
+```
+
+在UMyClass_RestrictedToClasses 的子类蓝图中测试效果：
+
+![Untitled](Untitled.png)
+
+在别的地方，比如关卡蓝图中测试效果：
+
+因此右键创建不出来，但是直接粘贴节点其实还是可以调用的。
+
+![Untitled](Untitled%201.png)
+
+## 源码中的例子：
+
+指定UBTFunctionLibrary中的节点，只能在BTNode中使用，否则没有意义。
+
+```cpp
+UCLASS(meta=(RestrictedToClasses="BTNode"), MinimalAPI)
+class UBTFunctionLibrary : public UBlueprintFunctionLibrary
+{
+UFUNCTION(BlueprintPure, Category="AI|BehaviorTree", Meta=(HidePin="NodeOwner", DefaultToSelf="NodeOwner"))
+	static AIMODULE_API UBlackboardComponent* GetOwnersBlackboard(UBTNode* NodeOwner);
+//....
+}
+```
+
+## 原理：
+
+```cpp
+static bool BlueprintActionFilterImpl::IsRestrictedClassMember(FBlueprintActionFilter const& Filter, FBlueprintActionInfo& BlueprintAction)
+{
+	bool bIsFilteredOut = false;
+	FBlueprintActionContext const& FilterContext = Filter.Context;
+	
+	if (UClass const* ActionClass = BlueprintAction.GetOwnerClass())
+	{
+		if (ActionClass->HasMetaData(FBlueprintMetadata::MD_RestrictedToClasses))
+		{
+			FString const& ClassRestrictions = ActionClass->GetMetaData(FBlueprintMetadata::MD_RestrictedToClasses);
+			
+			// Parse the the metadata into an array that is delimited by ',' and trim whitespace
+			TArray<FString> ParsedClassRestrictions;
+			ClassRestrictions.ParseIntoArray(ParsedClassRestrictions, TEXT(","));
+			for (FString& ValidClassName : ParsedClassRestrictions)
+			{
+				ValidClassName = ValidClassName.TrimStartAndEnd();
+			}
+
+			for (UBlueprint const* TargetContext : FilterContext.Blueprints)
+			{
+				UClass* TargetClass = TargetContext->GeneratedClass;
+				if(!TargetClass)
+				{
+					// Skip possible null classes (e.g. macros, etc)
+					continue;
+				}
+
+				bool bIsClassListed = false;
+				
+				UClass const* QueryClass = TargetClass;
+				// walk the class inheritance chain to see if this class is one
+				// of the allowed
+				while (!bIsClassListed && (QueryClass != nullptr))
+				{
+					FString const ClassName = QueryClass->GetName();
+					// If this class is on the list of valid classes
+					for (const FString& ValidClassName : ParsedClassRestrictions)
+					{
+						bIsClassListed = (ClassName == ValidClassName);
+						if (bIsClassListed)
+						{
+							break;
+						}
+					}
+					
+					QueryClass = QueryClass->GetSuperClass();
+				}
+				
+				// if the blueprint class wasn't listed as one of the few
+				// classes that this can be accessed from, then filter it out
+				if (!bIsClassListed)
+				{
+					bIsFilteredOut = true;
+					break;
+				}
+			}
+		}
+	}
+	
+	return bIsFilteredOut;
+}
+```