332 lines
14 KiB
Markdown
332 lines
14 KiB
Markdown
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# BlueprintProtected
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- **功能描述：** 指定该函数或属性只能在本类以及子类中被调用或读写，类似C++中的protected作用域限制。不可在别的蓝图类里访问。
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- **使用位置：** UFUNCTION, UPROPERTY
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- **引擎模块：** Blueprint
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- **元数据类型：** bool
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- **关联项：** [BlueprintPrivate](../BlueprintPrivate/BlueprintPrivate.md), [AllowPrivateAccess](../AllowPrivateAccess/AllowPrivateAccess.md)
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- **常用程度：** ★★★
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作用在函数上：
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标记该函数只能在本类以及子类中被调用，类似C++中的protected函数的作用域限制。不可在别的蓝图类里调用。
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作用在属性上时，标明该属性只能在本类或派生类里进行读写，但不能在别的蓝图类里访问。
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指定该函数或属性只能在本类以及子类中被调用或读写，类似C++中的protected函数的作用域限制。不可在别的蓝图类里访问。
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## 测试代码：
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```cpp
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UCLASS(Blueprintable, BlueprintType)
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class INSIDER_API AMyFunction_Access :public AActor
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{
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public:
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GENERATED_BODY()
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public:
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//(BlueprintProtected = true, ModuleRelativePath = Function/MyFunction_Access.h)
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//FUNC_Final | FUNC_Native | FUNC_Public | FUNC_BlueprintCallable
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UFUNCTION(BlueprintCallable, meta = (BlueprintProtected = "true"))
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void MyNative_HasProtected() {}
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//(BlueprintPrivate = true, ModuleRelativePath = Function/MyFunction_Access.h)
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//FUNC_Final | FUNC_Native | FUNC_Public | FUNC_BlueprintCallable
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UFUNCTION(BlueprintCallable, meta = (BlueprintPrivate = "true"))
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void MyNative_HasPrivate() {}
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public:
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//FUNC_Final | FUNC_Native | FUNC_Public | FUNC_BlueprintCallable
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UFUNCTION(BlueprintCallable)
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void MyNative_NativePublic() {}
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protected:
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//FUNC_Final | FUNC_Native | FUNC_Protected | FUNC_BlueprintCallable
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UFUNCTION(BlueprintCallable)
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void MyNative_NativeProtected() {}
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private:
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//FUNC_Final | FUNC_Native | FUNC_Private | FUNC_BlueprintCallable
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UFUNCTION(BlueprintCallable)
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void MyNative_NativePrivate() {}
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};
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```
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## 测试效果：
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蓝图中的子类（BPA_Access_Base继承自AMyFunction_Access ）效果：
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可见BlueprintProtected可以被子类调用，但是BlueprintPrivate只能在本类（C++类中定义的只能在C++中调用，蓝图中定义的只能在蓝图本类中调用）。而在C++中用protected或private修饰的函数会相应的增加FUNC_Protected和FUNC_Private，但是实际上并不会发生作用。因为机制的设计目的就是如此（详见后文解释）。
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而在BPA_Access_Base中直接定义的MyBPProtected和MyBPPrivate通过在函数细节面板上直接设置AccessSpecifier，可以在本类都可以调用，但是MyBPPrivate在更加的蓝图子类无法被调用。
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蓝图中的子类（BPA_Access_Child继承自BPA_Access_Base）效果：
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可见MyNative函数的访问一样。而MyBPPrivate则不能被调用了，这和我们预想的规则一样。
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而在外部类中(BPA_Access_Other，继承自Actor)，通过BPA_Access_Base或BPA_Access_Child对象实例访问函数的时候，发现带有BlueprintProtected和BlueprintPrivate都不能被调用。BP的函数也只有AccessSpecifier为默认Public的可以调用。这个规则也很符合预期。
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## 原理：
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在蓝图右键上是否可以选择该函数的过滤逻辑：
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如果是static函数，则总是可以。否则必须没有BlueprintProtected或BlueprintPrivate才可以是Public可以被选择出来的。
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如果是Private，则外部类必须是定义的类本身。
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如果是Protected，则外部类只需要是定义的类或子类。
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```cpp
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static bool BlueprintActionFilterImpl::IsFieldInaccessible(FBlueprintActionFilter const& Filter, FBlueprintActionInfo& BlueprintAction)
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{
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bool const bIsProtected = Field.HasMetaData(FBlueprintMetadata::MD_Protected);
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bool const bIsPrivate = Field.HasMetaData(FBlueprintMetadata::MD_Private);
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bool const bIsPublic = !bIsPrivate && !bIsProtected;
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if( !bIsPublic )
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{
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UClass const* ActionOwner = BlueprintAction.GetOwnerClass();
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for (UBlueprint const* Blueprint : FilterContext.Blueprints)
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{
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UClass const* BpClass = GetAuthoritativeBlueprintClass(Blueprint);
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if (!ensureMsgf(BpClass != nullptr
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, TEXT("Unable to resolve IsFieldInaccessible() - Blueprint (%s) missing an authoratative class (skel: %s, generated: %s, parent: %s)")
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, *Blueprint->GetName()
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, Blueprint->SkeletonGeneratedClass ? *Blueprint->SkeletonGeneratedClass->GetName() : TEXT("[NULL]")
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, Blueprint->GeneratedClass ? *Blueprint->GeneratedClass->GetName() : TEXT("[NULL]")
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, Blueprint->ParentClass ? *Blueprint->ParentClass->GetName() : TEXT("[NULL]")))
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{
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continue;
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}
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// private functions are only accessible from the class they belong to
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if (bIsPrivate && !IsClassOfType(BpClass, ActionOwner, /*bNeedsExactMatch =*/true))
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{
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bIsFilteredOut = true;
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break;
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}
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else if (bIsProtected && !IsClassOfType(BpClass, ActionOwner))
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{
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bIsFilteredOut = true;
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break;
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}
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}
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}
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}
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bool UEdGraphSchema_K2::ClassHasBlueprintAccessibleMembers(const UClass* InClass) const
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{
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// @TODO Don't show other blueprints yet...
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UBlueprint* ClassBlueprint = UBlueprint::GetBlueprintFromClass(InClass);
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if (!InClass->HasAnyClassFlags(CLASS_Deprecated | CLASS_NewerVersionExists) && (ClassBlueprint == NULL))
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{
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// Find functions
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for (TFieldIterator<UFunction> FunctionIt(InClass, EFieldIteratorFlags::IncludeSuper); FunctionIt; ++FunctionIt)
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{
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UFunction* Function = *FunctionIt;
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const bool bIsBlueprintProtected = Function->GetBoolMetaData(FBlueprintMetadata::MD_Protected);
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const bool bHidden = FObjectEditorUtils::IsFunctionHiddenFromClass(Function, InClass);
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if (UEdGraphSchema_K2::CanUserKismetCallFunction(Function) && !bIsBlueprintProtected && !bHidden)
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{
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return true;
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}
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}
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// Find vars
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for (TFieldIterator<FProperty> PropertyIt(InClass, EFieldIteratorFlags::IncludeSuper); PropertyIt; ++PropertyIt)
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{
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FProperty* Property = *PropertyIt;
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if (CanUserKismetAccessVariable(Property, InClass, CannotBeDelegate))
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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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在BP中定义的函数如果通过AccessSpecifier设置为Protected或Private，也会相应把该函数加上FUNC_Protected或FUNC_Private。从而实际上影响该函数的作用域。但源码中很多判断会先判断是否Native函数，如果是就不继续做限制。因此我们可以理解这是UE机制的有意为之，故意不把C++里的protected和private作用域算进去，而要求你必须自己手动显式的写上BlueprintProtected或BlueprintPrivate，这样避免有时的模糊不清。
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```cpp
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bool UEdGraphSchema_K2::CanFunctionBeUsedInGraph(const UClass* InClass, const UFunction* InFunction, const UEdGraph* InDestGraph, uint32 InAllowedFunctionTypes, bool bInCalledForEach, FText* OutReason) const
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{
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const bool bIsNotNative = !FBlueprintEditorUtils::IsNativeSignature(InFunction);
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if(bIsNotNative)
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{
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// Blueprint functions visibility flags can be enforced in blueprints - native functions
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// are often using these flags to only hide functionality from other native functions:
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const bool bIsProtected = (InFunction->FunctionFlags & FUNC_Protected) != 0;
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}
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bool UK2Node_CallFunction::IsActionFilteredOut(FBlueprintActionFilter const& Filter)
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{
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bool bIsFilteredOut = false;
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for(UEdGraph* TargetGraph : Filter.Context.Graphs)
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{
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bIsFilteredOut |= !CanPasteHere(TargetGraph);
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}
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if(const UFunction* TargetFunction = GetTargetFunction())
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{
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const bool bIsProtected = (TargetFunction->FunctionFlags & FUNC_Protected) != 0;
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const bool bIsPrivate = (TargetFunction->FunctionFlags & FUNC_Private) != 0;
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const UClass* OwningClass = TargetFunction->GetOwnerClass();
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if( (bIsProtected || bIsPrivate) && !FBlueprintEditorUtils::IsNativeSignature(TargetFunction) && OwningClass)
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{
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OwningClass = OwningClass->GetAuthoritativeClass();
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// we can filter private and protected blueprints that are unrelated:
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bool bAccessibleInAll = true;
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for (const UBlueprint* Blueprint : Filter.Context.Blueprints)
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{
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UClass* AuthoritativeClass = Blueprint->GeneratedClass;
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if(!AuthoritativeClass)
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{
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continue;
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}
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if(bIsPrivate)
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{
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bAccessibleInAll = bAccessibleInAll && AuthoritativeClass == OwningClass;
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}
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else if(bIsProtected)
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{
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bAccessibleInAll = bAccessibleInAll && AuthoritativeClass->IsChildOf(OwningClass);
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}
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}
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if(!bAccessibleInAll)
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{
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bIsFilteredOut = true;
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}
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}
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}
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return bIsFilteredOut;
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}
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```
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# 作用在属性上：
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作用在属性上时，标明该属性只能在本类或派生类里进行读写，但不能在别的蓝图类里访问。
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测试代码：
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```cpp
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UCLASS(Blueprintable, BlueprintType)
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class INSIDER_API AMyFunction_Access :public AActor
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{
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public:
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GENERATED_BODY()
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public:
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//(BlueprintProtected = true, Category = MyFunction_Access, ModuleRelativePath = Function/MyFunction_Access.h)
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//CPF_BlueprintVisible | CPF_ZeroConstructor | CPF_IsPlainOldData | CPF_NoDestructor | CPF_HasGetValueTypeHash | CPF_NativeAccessSpecifierPublic
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UPROPERTY(BlueprintReadWrite,meta = (BlueprintProtected = "true"))
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int32 MyNativeInt_HasProtected;
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//(BlueprintPrivate = true, Category = MyFunction_Access, ModuleRelativePath = Function/MyFunction_Access.h)
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//CPF_BlueprintVisible | CPF_ZeroConstructor | CPF_IsPlainOldData | CPF_NoDestructor | CPF_HasGetValueTypeHash | CPF_NativeAccessSpecifierPublic
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UPROPERTY(BlueprintReadWrite,meta = (BlueprintPrivate = "true"))
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int32 MyNativeInt_HasPrivate;
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public:
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//CPF_BlueprintVisible | CPF_ZeroConstructor | CPF_IsPlainOldData | CPF_NoDestructor | CPF_HasGetValueTypeHash | CPF_NativeAccessSpecifierPublic
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UPROPERTY(BlueprintReadWrite)
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int32 MyNativeInt_NativePublic;
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protected:
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//CPF_BlueprintVisible | CPF_ZeroConstructor | CPF_IsPlainOldData | CPF_NoDestructor | CPF_Protected | CPF_HasGetValueTypeHash | CPF_NativeAccessSpecifierProtected
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UPROPERTY(BlueprintReadOnly)
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int32 MyNativeInt_NativeProtected;
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private:
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//CPF_Edit | CPF_ZeroConstructor | CPF_IsPlainOldData | CPF_NoDestructor | CPF_HasGetValueTypeHash | CPF_NativeAccessSpecifierPrivate
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//error : BlueprintReadWrite should not be used on private members
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UPROPERTY(EditAnywhere)
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int32 MyNativeInt_NativePrivate;
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};
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```
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蓝图效果：
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在其子类BPA_Access_Base测试，发现除了MyNativeInt_HasPrivate都可以访问。这符合逻辑，毕竟Private的含义就是只有在本类才可以访问。
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而在本蓝图类定义的MyBPIntPrivate因为勾上了Private，会导致该属性增加了BlueprintPrivate = true的meta，但因为是本类里定义的，所以在本类里也依然可以读写访问。
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继续在蓝图中的子类（BPA_Access_Child继承自BPA_Access_Base）效果：
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Protected的属性依然都可以访问，但是MyBPIntPrivate属性因为是Private的，因此都不能读写，如果强制粘贴节点，会在编译的时候报错。Private的含义是只在本类中才可以访问。
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而在外部类中(BPA_Access_Other，继承自Actor)，通过BPA_Access_Base或BPA_Access_Child对象实例访问属性的时候：带有BlueprintProtected和BlueprintPrivate都不能访问。而C++中的protected修饰并无影响。
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而MyBPIntPrivate因为是Private所以不能访问。
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## 原理：
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在源码里搜索CPF_NativeAccessSpecifierProtected，发现并无使用的地方。
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而CPF_NativeAccessSpecifierPrivate只在IsPropertyPrivate中引用，后者也只在蓝图编译检测线程安全的时候被检测到。因此CPF_NativeAccessSpecifierPrivate也实际上并无真正的被用来做作用域的限制。
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综合二者，这也是在C++中protected和private并不在蓝图中造成影响的原因。但UHT会阻止private变量上的BlueprintReadWrite或BlueprintReadOnly，造成事实上的无法在蓝图中访问，达成了无法在蓝图子类里访问C++基类private变量的效果。
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因此实际上在蓝图中的变量作用域控制，采用的元数据BlueprintProtected 和BlueprintPrivate，在蓝图右键能否创建属性读写节点的逻辑在上面的BlueprintActionFilterImpl::IsFieldInaccessible函数中体现。而编译的时候判断一个属性是否可读写的逻辑在IsPropertyWritableInBlueprint和IsPropertyReadableInBlueprint这两个函数，如果最终的状态结果是Private，则说明不可访问。在UK2Node_VariableGet和UK2Node_VariableSet的ValidateNodeDuringCompilation，会检测出来并报错。
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```cpp
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bool FBlueprintEditorUtils::IsPropertyPrivate(const FProperty* Property)
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{
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return Property->HasAnyPropertyFlags(CPF_NativeAccessSpecifierPrivate) || Property->GetBoolMetaData(FBlueprintMetadata::MD_Private);
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}
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|
FBlueprintEditorUtils::EPropertyWritableState FBlueprintEditorUtils::IsPropertyWritableInBlueprint(const UBlueprint* Blueprint, const FProperty* Property)
|
|||
|
|
{
|
|||
|
|
if (Property)
|
|||
|
|
{
|
|||
|
|
if (!Property->HasAnyPropertyFlags(CPF_BlueprintVisible))
|
|||
|
|
{
|
|||
|
|
return EPropertyWritableState::NotBlueprintVisible;
|
|||
|
|
}
|
|||
|
|
if (Property->HasAnyPropertyFlags(CPF_BlueprintReadOnly))
|
|||
|
|
{
|
|||
|
|
return EPropertyWritableState::BlueprintReadOnly;
|
|||
|
|
}
|
|||
|
|
if (Property->GetBoolMetaData(FBlueprintMetadata::MD_Private))
|
|||
|
|
{
|
|||
|
|
const UClass* OwningClass = Property->GetOwnerChecked<UClass>();
|
|||
|
|
if (OwningClass->ClassGeneratedBy.Get() != Blueprint)
|
|||
|
|
{
|
|||
|
|
return EPropertyWritableState::Private;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
return EPropertyWritableState::Writable;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
FBlueprintEditorUtils::EPropertyReadableState FBlueprintEditorUtils::IsPropertyReadableInBlueprint(const UBlueprint* Blueprint, const FProperty* Property)
|
|||
|
|
{
|
|||
|
|
if (Property)
|
|||
|
|
{
|
|||
|
|
if (!Property->HasAnyPropertyFlags(CPF_BlueprintVisible))
|
|||
|
|
{
|
|||
|
|
return EPropertyReadableState::NotBlueprintVisible;
|
|||
|
|
}
|
|||
|
|
if (Property->GetBoolMetaData(FBlueprintMetadata::MD_Private))
|
|||
|
|
{
|
|||
|
|
const UClass* OwningClass = Property->GetOwnerChecked<UClass>();
|
|||
|
|
if (OwningClass->ClassGeneratedBy.Get() != Blueprint)
|
|||
|
|
{
|
|||
|
|
return EPropertyReadableState::Private;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
return EPropertyReadableState::Readable;
|
|||
|
|
}
|
|||
|
|
```
|