UE网络-WithIdenticalViaEquality详解

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WithIdenticalViaEquality是什么

在属性同步时候, 如果想自定义比较函数应该怎么处理呢? WithIdenticalViaEquality就是表明该结构体使用Operator ==进行比较. 注意它和WithIdentical互斥.

自定义结构体指定WithIdenticalViaEquality

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USTRUCT()
struct FTestNetSerializeSharedPtrContainer
{
    GENERATED_USTRUCT_BODY()

    uint32 CounterUniqueID = 0;
    TSharedPtr<FTestNetSerializeSharedPtrBase> Data;

    /** Serialize the root motion sources and their states for this group */
    bool NetSerialize(FArchive& Ar, UPackageMap* Map, bool& bOutSuccess);

    bool Identical(const FTestNetSerializeSharedPtrContainer* Other, uint32 PortFlags) const;
    bool operator==(const FTestNetSerializeSharedPtrContainer &Other) const;
    bool operator!=(const FTestNetSerializeSharedPtrContainer& Other) const;

    void AddStructReferencedObjects(class FReferenceCollector& Collector);
};

template<>
struct TStructOpsTypeTraits< FTestNetSerializeSharedPtrContainer > : public TStructOpsTypeTraitsBase2< FTestNetSerializeSharedPtrContainer >
{
    enum
    {
        WithNetSerializer = true,
        WithIdenticalViaEquality = true,
        WithCopy = true,
        WithAddStructReferencedObjects = true
    };
};

将WithIdenticalViaEquality映射到EStructFlags::STRUCT_IdenticalNative

构建UScriptStruct

在PreInit时候,构建UScriptStruct

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将WithIdenticalViaEquality属性映射到EStructFlags::STRUCT_IdenticalNative

构建UScriptStruct, 通过模板, 指定WithIdenticalViaEquality属性.

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img

好了, 到此为止, 已经将我们指定的WithIdenticalViaEquality映射到EStructFlags::STRUCT_IdenticalNative上了. 即UScriptStruct.StructFlags已经包含EStructFlags::STRUCT_IdenticalNative属性.

在比较中使用自定义比较函数

堆栈:

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--UActorChannel.ReplicateActor.if.{ 
 |--FObjectReplicator.ReplicateProperties 
 | |--FNetSerializeCB.UpdateChangelistMgr 
 | | |--FRepLayout.UpdateChangelistMgr 
 | | | |--FRepLayout.CompareProperties.else 
 | | | | |--CompareParentProperties.if.else 
 | | | | | |--UE4_RepLayout_Private.CompareParentPropertyHelper 
 | | | | | | |--CompareParentProperty 
 | | | | | | | |--CompareProperties_r.for 
 | | | | | | | | |--FStructProperty.Identical

在进行属性比较的时候调用PropertiesAreIdentical:

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调用Struct的比较函数:UScriptStruct::CompareScriptStruct, 因为有标志位:STRUCT_IdenticalNative, 所以进行自定义比较.

调用UScriptStruct.TCppStructOps.Identical, 因为是类型WithIdenticalViaEquality, 所以最终调用了operator==

image-20240418173609829

最终调用了自定义operator==函数.