98 lines
3.7 KiB
Markdown
98 lines
3.7 KiB
Markdown
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# DontUseGenericSpawnObject
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- **功能描述：** 阻止使用蓝图中的Generic Create Object节点来生成本类的对象。
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- **使用位置：** UCLASS
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- **引擎模块：** Blueprint
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- **元数据类型：** bool
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- **限制类型：** 既非Actor又非ActorComponent的BluprintType类时
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- **常用程度：** ★★
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用于阻止该类被通用的ConstructObject蓝图节点所构造出来。在源码里典型里使用例子是UDragDropOperation和UUserWidget，前者由UK2Node_CreateDragDropOperation这个专门的节点建出来（内部调用UWidgetBlueprintLibrary::CreateDragDropOperation），后者由CreateWidget创建。因此这种的典型用法是你自己再创建一个New的函数来自己创建该Object。
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## 测试代码：
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```cpp
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UCLASS(Blueprintable,meta=(DontUseGenericSpawnObject="true"))
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class INSIDER_API UMyClass_CustomSpawnObject :public UObject
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{
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GENERATED_BODY()
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public:
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UPROPERTY(BlueprintReadWrite,EditAnywhere)
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float MyFloat;
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UFUNCTION(BlueprintCallable)
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static UMyClass_CustomSpawnObject* CreateMyClassObjectByMyOwnSpawn(float value)
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{
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UMyClass_CustomSpawnObject* obj= NewObject<UMyClass_CustomSpawnObject>();
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obj->MyFloat=value;
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return obj;
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}
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};
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```
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## 测试效果：
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## 原理：
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会提前验证是否包含DontUseGenericSpawnObject元数据，因为是采用GetBoolMetaData，因此必须写上=”true”
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```cpp
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struct FK2Node_GenericCreateObject_Utils
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{
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static bool CanSpawnObjectOfClass(TSubclassOf<UObject> ObjectClass, bool bAllowAbstract)
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{
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// Initially include types that meet the basic requirements.
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// Note: CLASS_Deprecated is an inherited class flag, so any subclass of an explicitly-deprecated class also cannot be spawned.
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bool bCanSpawnObject = (nullptr != *ObjectClass)
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&& (bAllowAbstract || !ObjectClass->HasAnyClassFlags(CLASS_Abstract))
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&& !ObjectClass->HasAnyClassFlags(CLASS_Deprecated | CLASS_NewerVersionExists);
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// UObject is a special case where if we are allowing abstract we are going to allow it through even though it doesn't have BlueprintType on it
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if (bCanSpawnObject && (!bAllowAbstract || (*ObjectClass != UObject::StaticClass())))
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{
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static const FName BlueprintTypeName(TEXT("BlueprintType"));
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static const FName NotBlueprintTypeName(TEXT("NotBlueprintType"));
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static const FName DontUseGenericSpawnObjectName(TEXT("DontUseGenericSpawnObject"));
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auto IsClassAllowedLambda = [](const UClass* InClass)
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{
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return InClass != AActor::StaticClass()
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&& InClass != UActorComponent::StaticClass();
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};
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// Exclude all types in the initial set by default.
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bCanSpawnObject = false;
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const UClass* CurrentClass = ObjectClass;
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// Climb up the class hierarchy and look for "BlueprintType." If "NotBlueprintType" is seen first, or if the class is not allowed, then stop searching.
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while (!bCanSpawnObject && CurrentClass != nullptr && !CurrentClass->GetBoolMetaData(NotBlueprintTypeName) && IsClassAllowedLambda(CurrentClass))
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{
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// Include any type that either includes or inherits 'BlueprintType'
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bCanSpawnObject = CurrentClass->GetBoolMetaData(BlueprintTypeName);
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// Stop searching if we encounter 'BlueprintType' with 'DontUseGenericSpawnObject'
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if (bCanSpawnObject && CurrentClass->GetBoolMetaData(DontUseGenericSpawnObjectName))
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{
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bCanSpawnObject = false;
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break;
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}
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CurrentClass = CurrentClass->GetSuperClass();
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}
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// If we validated the given class, continue walking up the hierarchy to make sure we exclude it if it's an Actor or ActorComponent derivative.
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while (bCanSpawnObject && CurrentClass != nullptr)
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{
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bCanSpawnObject &= IsClassAllowedLambda(CurrentClass);
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CurrentClass = CurrentClass->GetSuperClass();
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}
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}
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return bCanSpawnObject;
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}
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};
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```
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