2.1 UE4反射分析-空AActor拆解

Ophelia ·

更新时间:2024-09-21

· 797 次阅读

一、创建一个继承自AActor的空类AMyActor，对GENERATED_BODY()宏Alt+G不断深入(需安装Visual Assist) 二、展开GENERATED_BODY() 2.1、第一次展开

//GENERATED_BODY()展开后
CURRENT_FILE_ID___LINE___GENERATED_BODY
//再次替换后
Reflect_Source_Reflect_Public_MyActor_h_12_GENERATED_BODY

2.2、将Reflect_Source_Reflect_Public_MyActor_h_12_GENERATED_BODY宏再次展开

public:
	Reflect_Source_Reflect_Public_MyActor_h_12_PRIVATE_PROPERTY_OFFSET		//空
	Reflect_Source_Reflect_Public_MyActor_h_12_RPC_WRAPPERS_NO_PURE_DECLS	//空
	Reflect_Source_Reflect_Public_MyActor_h_12_INCLASS_NO_PURE_DECLS		//2.1
	Reflect_Source_Reflect_Public_MyActor_h_12_ENHANCED_CONSTRUCTORS		//2.2

三、依次展开以上四个宏 3.1 将Reflect_Source_Reflect_Public_MyActor_h_12_INCLASS_NO_PURE_DECLS宏替换

第一部分private功能：

注册C++原生函数
构建对应UClass的辅助结构体

第二部分public功能：

提供基础特征(类似Traits)：ThisClass、Super、ClassFlag、CastFlag、OwnerPacket，new()(仅供编辑器内部使用)
重载 << 实现类的代理序列化

private:
	//注册C++原生函数以暴露给蓝图虚拟机使用?
	static void StaticRegisterNativesAMyActor();
	//为了构建对应的UClass，是一个辅助结构体
	friend struct Z_Construct_UClass_AMyActor_Statics;
public:
	DECLARE_CLASS(AMyActor, AActor, COMPILED_IN_FLAGS(0), CASTCLASS_None, TEXT("/Script/Reflect"), NO_API)
	DECLARE_SERIALIZER(AMyActor)

3.1.1 展开 DECLARE_CLASS(AMyActor, AActor, COMPILED_IN_FLAGS(0), CASTCLASS_None, TEXT("/Script/Reflect"), NO_API)

//#define DECLARE_CLASS( TClass, TSuperClass, TStaticFlags, TStaticCastFlags, TPackage, TRequiredAPI  )
//TPackage:包所在路径
//TStaticFlags:类属性标记 EClassFlags(0: 默认，不带任何其他属性)
//TStaticCastFlags:类的Cast规则(CASTCLASS_None: 不能转换为默认类型)
//TRequiredAPI：Dll导出宏(NO_API: 导出时直接为exe运行，而不用链接API)
//3.1：赋值
private:
	//禁止外界使用 '='
	AMyActor& operator=(AMyActor&&);
	AMyActor& operator=(const AMyActor&);
	//生成一个自己的UClass
	NO_API static UClass* GetPrivateStaticClass();
public:
	/** Bitwise union of #EClassFlags pertaining to this class.*/
	//与该类有关的#EClassFlags的按位并集?
	enum { StaticClassFlags = 0 };
	/** Typedef for the base class ({{ typedef-type }}) */
	typedef AActor Super;
	/** Typedef for {{ typedef-type }}. */
	typedef AMyActor ThisClass;
	/** Returns a UClass object representing this class at runtime */
	//返回所属的类
	inline static UClass* StaticClass()
	{
		return GetPrivateStaticClass();
	}
	/** Returns the package this class belongs in */
	//返回所属的包
	inline static const TCHAR* StaticPackage()
	{
		return TEXT("/Script/Reflect");
	}
	/** Returns the static cast flags for this class */
	//返回类Cast规则的标记
	inline static EClassCastFlags StaticClassCastFlags()
	{
		return CASTCLASS_None;
	}
	//重载了new 类似NewObject，但仅供引擎使用
	/** For internal use only; use StaticConstructObject() to create new objects. */
	inline void* operator new(const size_t InSize, EInternal InInternalOnly, UObject * InOuter = (UObject*)GetTransienTEXT("/Script/Reflect")(), FName InName = NAME_None, EObjectFlags InSetFlags = RF_NoFlags)
	{
		return StaticAllocateObject(StaticClass(), InOuter, InName, InSetFlags);
	}
	/** For internal use only; use StaticConstructObject() to create new objects. */
	inline void* operator new(const size_t InSize, EInternal * InMem)
	{
		return (void*)InMem;
	}

3.1.2 展开 DECLARE_SERIALIZER(AMyActor)

//重载<<，序列化自己
friend FArchive& operator<<(FArchive & Ar, AMyActor * &Res)
{
	return Ar << (UObject*&)Res;
}
friend void operator<<(FStructuredArchive::FSlot InSlot, AMyActor * &Res)
{
	InSlot << (UObject*&)Res;
}

3.2 将Reflect_Source_Reflect_Public_MyActor_h_12_ENHANCED_CONSTRUCTORS宏展开

主要功能：

private: 关闭移动、拷贝构造功能
public: 提供热更新支持

//四
private:
	/** Private move- and copy-constructors, should never be used */
	//防止移动、拷贝构造
	NO_API AMyActor(AMyActor&&);
	NO_API AMyActor(const AMyActor&);
public:
	//热更新,自行展开
	DECLARE_VTABLE_PTR_HELPER_CTOR(NO_API, AMyActor);
	DEFINE_VTABLE_PTR_HELPER_CTOR_CALLER(AMyActor);
	DEFINE_DEFAULT_CONSTRUCTOR_CALL(AMyActor);
private:

四.总结空AActor中的GENERATED_BODY()功能

private:

注册C++原生函数给蓝图虚拟机提供构建UClass对应的结构体关闭移动、拷贝构造函数

public:

提供Actor基础标识：ThisClass、Super、Flags，OwnerPacket，重载类的new() 重载<<实现序列化提供热重载功能 五、打开自动生成的MyActor.gen.cpp类

在这里插入图片描述

// Fill out your copyright notice in the Description page of Project Settings.
#include "test1.h"
#include "UObject/GeneratedCppIncludes.h"
#include "Reflect/Public/MyActor.h"
#ifdef _MSC_VER
#pragma warning (push)
#pragma warning (disable : 4883)
#endif
#if NoneAll
/**
 * 一：外部模块执行Z_Construct_UClass_AMyActor构造类
 */ 
//生成的MyActor代码的空链接函数?
void EmptyLinkFunctionForGeneratedCodeMyActor()
{
}
// Cross Module References
//构造AMyActor对应的UClass的UClass对象，无注册
REFLECT_API UClass* Z_Construct_UClass_AMyActor_NoRegister();
UClass* Z_Construct_UClass_AMyActor_NoRegister()
{
	return AMyActor::StaticClass();
}
//构造AMyActor对应的UClass的UClass对象，有注册
REFLECT_API UClass* Z_Construct_UClass_AMyActor();
UClass* Z_Construct_UClass_AMyActor()
{
	//使用ConstructUClass构造UClass
	static UClass* OuterClass = nullptr;
	if (!OuterClass)
	{
		UE4CodeGen_Private::ConstructUClass(OuterClass, Z_Construct_UClass_AMyActor_Statics::ClassParams);
	}
	return OuterClass;
}
//5.1 构造所在包的UPackage对象
UPackage* Z_Construct_UPackage__Script_Reflect();
/******** 核心：构造UClass ************start**********/
#if 1
ENGINE_API UClass* Z_Construct_UClass_AActor();
//定义辅助构造UClass的结构体
struct Z_Construct_UClass_AMyActor_Statics
{
	//负责构建UClass和UPackage
	static UObject* (* const DependentSingletons[])();
	//元数据参数
#if WITH_METADATA
	//包含模组相对路径、包含路径
	static const UE4CodeGen_Private::FMetaDataPairParam Class_MetaDataParams[];
#endif
	//类的特性：抽象 (TCppClassTypeTraits::IsAbstract)
	static const FCppClassTypeInfoStatic StaticCppClassTypeInfo;
	//Z_Construct_UClass_AMyActor_Statics的核心、存放类的各项参数
	//上面的所有参数都会赋值到ClassParams中(DependentSingletons、Class_MetaDataParams、StaticCppClassTypeInfo
	static const UE4CodeGen_Private::FClassParams ClassParams;
};
//初始化DependentSingletons 构造父类的UClass和Package
UObject* (* const Z_Construct_UClass_AMyActor_Statics::DependentSingletons[])() = {
	(UObject * (*)())Z_Construct_UClass_AActor,
	(UObject * (*)())Z_Construct_UPackage__Script_Reflect,
};
//初始化Class_MetaDataParams[] 元数据构造数组，提供包含路径和模组的相对路径
#if WITH_METADATA
const UE4CodeGen_Private::FMetaDataPairParam Z_Construct_UClass_AMyActor_Statics::Class_MetaDataParams[] = {
	{ "IncludePath", "MyActor.h" },
	{ "ModuleRelativePath", "Public/MyActor.h" },
};
#endif
//定义c++类的特性，这里定义为抽象
const FCppClassTypeInfoStatic Z_Construct_UClass_AMyActor_Statics::StaticCppClassTypeInfo = {
	TCppClassTypeTraits::IsAbstract,
};
//初始化ClassParams 
const UE4CodeGen_Private::FClassParams Z_Construct_UClass_AMyActor_Statics::ClassParams = {
	//ARRAY_COUNT:获取数组数量
	&AMyActor::StaticClass,						//=ClassNoRegisterFunc
	nullptr,									//UTF8格式的配置名字?
	&StaticCppClassTypeInfo,					//c++特定类型的特性，在.h中定义为IsAbstrct
	DependentSingletons,						//绑定函数指针：DependencySingletonFuncArray
	nullptr,									//函数数组(UFUNCTION)
	nullptr,									//成员变量数组(UPROPERTY)
	nullptr,									//Implement实现接口数组
	ARRAY_COUNT(DependentSingletons),			//NumDependencySingletons
	0,											//数组数量
	0,											//成员变量数量
	0,											//Implement实现接口数量
	0x009000A0u,								//类标记
	//元数据数组和其数量，服务于编辑器
	METADATA_PARAMS(Z_Construct_UClass_AMyActor_Statics::Class_MetaDataParams, ARRAY_COUNT(Z_Construct_UClass_AMyActor_Statics::Class_MetaDataParams))
};
#endif
/************* 核心：构造UClass ***********end***********/
// End Cross Module References
//静态注册——下文中GetPrivateStaticClass最终调用的注册函数
void AMyActor::StaticRegisterNativesAMyActor()
{
}
IMPLEMENT_CLASS(AMyActor, 1586330386);
{
	//一 展开IMPLEMENT_CLASS(AMyActor, 1586330386)
	//#define IMPLEMENT_CLASS(TClass, TClassCrc) 
	//延迟注册
	static TClassCompiledInDefer AutoInitializeAMyActor(TEXT("AMyActor"), sizeof(AMyActor), AMyActorCrc); 
	//获取到类对应的UClass
	UClass* AMyActor::GetPrivateStaticClass() 
	{ 
		static UClass* PrivateStaticClass = NULL; 
		if (!PrivateStaticClass) 
		{ 
			/* this could be handled with templates, but we want it external to avoid code bloat */ 
			GetPrivateStaticClassBody( 
				StaticPackage(), 
				(TCHAR*)TEXT("AMyActor") + 1 + ((StaticClassFlags & CLASS_Deprecated) ? 11 : 0), 
				PrivateStaticClass, 
				StaticRegisterNatives##AMyActor, 
				sizeof(AMyActor), 
				alignof(AMyActor), 
				(EClassFlags)AMyActor::StaticClassFlags, 
				AMyActor::StaticClassCastFlags(), 
				AMyActor::StaticConfigName(), 
				(UClass::ClassConstructorType)InternalConstructor, 
				(UClass::ClassVTableHelperCtorCallerType)InternalVTableHelperCtorCaller, 
				&AMyActor::AddReferencedObjects, 
				&AMyActor::Super::StaticClass, 
				&AMyActor::WithinClass::StaticClass 
			); 
		} 
		return PrivateStaticClass; 
	}
}
template REFLECT_API UClass* StaticClass()
{
	return AMyActor::StaticClass();
}
//编辑器运行时调用的构造(Z_Construct_UClass_AMyActor)并注册(StaticClass)UClass函数
static FCompiledInDefer Z_CompiledInDefer_UClass_AMyActor(Z_Construct_UClass_AMyActor, &AMyActor::StaticClass, TEXT("/Script/Reflect"), TEXT("AMyActor"), false, nullptr, nullptr, nullptr);
DEFINE_VTABLE_PTR_HELPER_CTOR(AMyActor); {
	//一
	//热更新函数实现
	AMyActor::AMyActor(FVTableHelper& Helper)
		: Super(Helper) 
	{};
}

5.1 Z_Construct_UPackage__Script_Reflect()的实现

封装所在包的信息(FPackageParams )后返回对应UPackage

UPackage* Z_Construct_UPackage__Script_Reflect()
{
	static UPackage* ReturnPackage = nullptr;
	if (!ReturnPackage)
	{
		static const UE4CodeGen_Private::FPackageParams PackageParams = {
			"/Script/Reflect",				//NameUTF8
			nullptr,						//UObject* (* const* SingletonFuncArray)();
			0,								//NumSingletons
			PKG_CompiledIn | 0x00000000,	//PackageFlags
			0x12C9A2B2,						//BodyCRC
			0x638DBBFE,						//DeclarationsCRC
			METADATA_PARAMS(nullptr, 0)		//元数据数组以及其数量：MetaDataArray，NumMetaData
		};
		//通过上述参数构造UPackage
		UE4CodeGen_Private::ConstructUPackage(ReturnPackage, PackageParams);
		}
		return ReturnPackage;
	}

六、代码总结： 6.1 GENERATED_BODY()宏

展开后共：

Reflect_Source_Reflect_Public_MyActor_h_11_PRIVATE_PROPERTY_OFFSET
Reflect_Source_Reflect_Public_MyActor_h_11_RPC_WRAPPERS_NO_PURE_DECLS
Reflect_Source_Reflect_Public_MyActor_h_11_INCLASS_NO_PURE_DECLS
Reflect_Source_Reflect_Public_MyActor_h_11_ENHANCED_CONSTRUCTORS

四种宏，展开后第一和第二个宏暂时为空

6.1.1 Reflect_Source_Reflect_Public_MyActor_h_11_INCLASS_NO_PURE_DECLS 主要功能

1、声明部分cpp函数、结构体
2、提供基本Traits (禁用 = ，GetPrivateStaticClass，StaticClassFlags，Super，ThisClass，StaticClass，StaticPackage，StaticClassCastFlags，operator new() )
3、代理序列化 operator<<

6.1.2 Reflect_Source_Reflect_Public_MyActor_h_12_ENHANCED_CONSTRUCTORS主要功能

1、禁止外界使用移动、拷贝构造函数
2、热更新支持
3、提供构造函数包装器

6.2 MyActor.gen.cpp

自动生成的gen.cpp内代码主要用于

构造并注册UClass

注册C++原生函数以暴露给蓝图虚拟机
构建类对应UClass的辅助结构体
GetPrivateStaticClass()
Z_CompiledInDefer_UClass_AMyActor();

部分GENERATED_BODY中声明函数的实现。

七、XMind逻辑分析

空AActor反射生成代码分析 XMind

作者：卅秋

反射 ue4 ue

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