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

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+# UnsafeDuringActorConstruction
+
+- **功能描述：** 标明该函数不能在Actor的构造函数里调用
+- **使用位置：** UFUNCTION
+- **引擎模块：** Blueprint
+- **元数据类型：** bool
+- **常用程度：** ★★
+
+标明该函数不能在Actor的构造函数里调用。一般是涉及渲染及物理的函数，在Actor的构造期间不允许被调用。
+
+## 测试代码：
+
+```cpp
+UCLASS(Blueprintable, BlueprintType)
+class INSIDER_API UMyFunction_Unsafe :public UBlueprintFunctionLibrary
+{
+public:
+	GENERATED_BODY()
+public:
+	UFUNCTION(BlueprintCallable)
+	static void MySafeFunction();
+	UFUNCTION(BlueprintCallable, meta=(UnsafeDuringActorConstruction = "true"))
+	static void MyUnsafeFunction();
+};
+```
+
+在蓝图里函数的细节面板上也可以设置该Meta：UnsafeDuringActorConstruction，和在C++里设置是一样的效果。
+
+可以发现MyUnsafeFunction函数不能在Actor构造函数里被调用出来，而蓝图里自定义的函数加上UnsafeDuringActorConstruction 标志后也会生成相应的警告和编译错误信息。
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+在蓝图中有该系列的判断，一目了然。
+
+```cpp
+bool UEdGraphSchema_K2::CanFunctionBeUsedInGraph(const UClass* InClass, const UFunction* InFunction, const UEdGraph* InDestGraph, uint32 InAllowedFunctionTypes, bool bInCalledForEach, FText* OutReason) const
+{
+const bool bIsUnsafeForConstruction = InFunction->GetBoolMetaData(FBlueprintMetadata::MD_UnsafeForConstructionScripts);	
+if (bIsUnsafeForConstruction && bIsConstructionScript)
+{
+	if(OutReason != nullptr)
+	{
+		*OutReason = LOCTEXT("FunctionUnsafeForConstructionScript", "Function cannot be used in a Construction Script.");
+	}
+
+	return false;
+}
+}
+```