96 lines
3.1 KiB
Markdown
96 lines
3.1 KiB
Markdown
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# Blueprintable
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- **功能描述：** 可以在蓝图里被继承，隐含的作用也可当变量类型
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- **引擎模块：** Blueprint
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- **元数据类型：** bool
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- **作用机制：** 在Meta添加[IsBlueprintBase](../../../../Meta/Blueprint/IsBlueprintBase.md)和[BlueprintType](../../../../Meta/Blueprint/BlueprintType.md)
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- **关联项：** [NotBlueprintable](../NotBlueprintable.md)
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- **常用程度：** ★★★★★
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可以在蓝图里被继承，隐含的作用也可当变量类型。
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当设置Blueprintable标记的时候，会隐含的设置上BlueprintType = true的metadata。去除的时候，也会相应的去除掉BlueprintType = true。
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## 示例代码：
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```cpp
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/*
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(BlueprintType = true, IncludePath = Class/MyClass_Blueprintable.h, IsBlueprintBase = true, ModuleRelativePath = Class/MyClass_Blueprintable.h)
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*/
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UCLASS(Blueprintable)
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class INSIDER_API UMyClass_Blueprintable :public UObject
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{
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GENERATED_BODY()
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};
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/*
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(IncludePath = Class/MyClass_Blueprintable.h, IsBlueprintBase = false, ModuleRelativePath = Class/MyClass_Blueprintable.h)
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*/
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UCLASS(NotBlueprintable)
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class INSIDER_API UMyClass_NotBlueprintable :public UObject
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{
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GENERATED_BODY()
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};
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/*
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(BlueprintType = true, IncludePath = Class/MyClass_Blueprintable.h, IsBlueprintBase = true, ModuleRelativePath = Class/MyClass_Blueprintable.h)
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*/
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UCLASS(Blueprintable)
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class INSIDER_API UMyClass_NotBlueprintable_To_Blueprintable :public UMyClass_NotBlueprintable
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{
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GENERATED_BODY()
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};
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/*
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(IncludePath = Class/MyClass_Blueprintable.h, IsBlueprintBase = false, ModuleRelativePath = Class/MyClass_Blueprintable.h)
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*/
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UCLASS(NotBlueprintable)
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class INSIDER_API UMyClass_Blueprintable_To_NotBlueprintable :public UMyClass_Blueprintable
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{
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GENERATED_BODY()
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};
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```
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## 示例效果：
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只有带有Blueprintable才可以被选做基类。
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不过是否能够当做变量的规则，还是会依赖父类的Blueprint标记。因此以下这3个都是可以当做变量的。
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其中UMyClass_Blueprintable_To_NotBlueprintable可以当做变量是因为父类UMyClass_Blueprintable可以当做变量，因此就继承了下来。
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## 原理：
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可见MD_IsBlueprintBase的判断用来决定是否能创建子类
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```cpp
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bool FKismetEditorUtilities::CanCreateBlueprintOfClass(const UClass* Class)
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{
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bool bCanCreateBlueprint = false;
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if (Class)
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{
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bool bAllowDerivedBlueprints = false;
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GConfig->GetBool(TEXT("Kismet"), TEXT("AllowDerivedBlueprints"), /*out*/ bAllowDerivedBlueprints, GEngineIni);
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bCanCreateBlueprint = !Class->HasAnyClassFlags(CLASS_Deprecated)
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&& !Class->HasAnyClassFlags(CLASS_NewerVersionExists)
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&& (!Class->ClassGeneratedBy || (bAllowDerivedBlueprints && !IsClassABlueprintSkeleton(Class)));
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const bool bIsBPGC = (Cast<UBlueprintGeneratedClass>(Class) != nullptr);
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const bool bIsValidClass = Class->GetBoolMetaDataHierarchical(FBlueprintMetadata::MD_IsBlueprintBase)
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|| (Class == UObject::StaticClass())
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|| (Class == USceneComponent::StaticClass() || Class == UActorComponent::StaticClass())
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|| bIsBPGC; // BPs are always considered inheritable
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bCanCreateBlueprint &= bIsValidClass;
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}
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return bCanCreateBlueprint;
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}
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```
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