67 lines
2.3 KiB
Markdown
67 lines
2.3 KiB
Markdown
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# BlueprintInternalUseOnlyHierarchical
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- **功能描述：** 在BlueprintInternalUseOnly的基础上，增加了子类也不能定义新BP变量的限制。
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- **元数据类型：** bool
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- **引擎模块：** Blueprint
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- **作用机制：** 在Meta中加入[BlueprintInternalUseOnlyHierarchical](../../../Meta/Blueprint/BlueprintInternalUseOnlyHierarchical.md)
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- **常用程度：★**
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在BlueprintInternalUseOnly的基础上，增加了子类也不能定义新BP变量的限制。
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目前只找到一个用处，但是也依然没有子类。如果我们在C++中定义新的子类，则所有的子类都不能定义变量。注意和FTableRowBase的区别是，FTableRowBase的子类依然可以定义新变量，因为FTableRowBase的BlueprintInternalUseOnly标记只作用于自己。
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## 示例代码：
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```cpp
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USTRUCT(BlueprintInternalUseOnlyHierarchical)
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struct GAMEPLAYABILITIESEDITOR_API FGameplayAbilityAuditRow : public FTableRowBase
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{}
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USTRUCT(BlueprintInternalUseOnly)
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struct FTableRowBase
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{}
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```
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## 原理：
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只在这个地方用到，GetBoolMetaDataHierarchical会检查结构的所有父类测试是否含有某个标记。所以只要有一个父类有一个这个标记，就不能定义新变量。
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```cpp
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bool UEdGraphSchema_K2::IsAllowableBlueprintVariableType(const UScriptStruct* InStruct, const bool bForInternalUse)
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{
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if (const UUserDefinedStruct* UDStruct = Cast<const UUserDefinedStruct>(InStruct))
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{
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if (EUserDefinedStructureStatus::UDSS_UpToDate != UDStruct->Status.GetValue())
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{
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return false;
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}
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// User-defined structs are always allowed as BP variable types.
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return true;
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}
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// struct needs to be marked as BP type
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if (InStruct && InStruct->GetBoolMetaDataHierarchical(FBlueprintMetadata::MD_AllowableBlueprintVariableType))
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{
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// for internal use, all BP types are allowed
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if (bForInternalUse)
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{
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return true;
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}
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// for user-facing use case, only allow structs that don't have the internal-use-only tag
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// struct itself should not be tagged
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if (!InStruct->GetBoolMetaData(FBlueprintMetadata::MD_BlueprintInternalUseOnly))
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{
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// struct's base structs should not be tagged
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if (!InStruct->GetBoolMetaDataHierarchical(FBlueprintMetadata::MD_BlueprintInternalUseOnlyHierarchical))
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{
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return true;
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}
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}
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}
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return false;
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}
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```
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