重点：

1.将要创建的类管理起来，当面临一类构件的注册管理的实现。

2.包括调用函数内部类方法。

一：定义结构体和基类

Define.h

enum class MyType
{red,blue,green,black
};class BaseTool
{
public:BaseTool() = default;virtual ~BaseTool()=default;private:};

二：设计单例管理类

RegMananger.h

#pragma once
#include "Define.h"
#include <iostream>
#include <cstdarg>
#include <set>class ICreator
{
public:virtual ~ICreator() {}virtual std::shared_ptr<BaseTool> Create() = 0;
};//单例管理注册信息
class RegMananger
{
public:static RegMananger& Getinstance();RegMananger(const RegMananger&) = delete;RegMananger& operator=(const RegMananger&) = delete;public:void AddMananger(MyType type, ICreator* create);std::shared_ptr<BaseTool> GetEditor(MyType type);
private:RegMananger();~RegMananger();//保证类的私密性struct Impl;Impl* m_pData;
};//计算可变参数个数，限制在20个
#define ARG_T(t)  t  //解决VC编译错误
#define ARG_N(a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12,a13,a14,a15,a16,a17,a18,a19,a20,N,...)  N //截取并返回第四个参数，这里限制了可变参数计算的范围［1，4］
#define ARG_N_HELPER(...)  ARG_T(ARG_N(__VA_ARGS__))   //辅助宏
#define COUNT_ARG(...)  ARG_N_HELPER(__VA_ARGS__,20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0)  //返回可变参数个数//注册宏函数
#define REG_TOOL(CLASSNAME, ...) \
class AutoReg##CLASSNAME :public ICreator \
{ \
public:\AutoReg##CLASSNAME()\{\std::set<MyType>&& typeSet{GetType(COUNT_ARG(__VA_ARGS__),__VA_ARGS__)};\for (auto& var:typeSet)\{\RegMananger::Getinstance().AddMananger(var,this);\}\}\
public:	\virtual std::shared_ptr<BaseTool> Create() override	\{	\return std::make_shared<BaseTool>();	\}	\
private: \std::set<MyType> GetType(int n, ...)\{\std::set<MyType> myType; \va_list args; \va_start(args, n); \while (n--)\{\MyType ty = va_arg(args, MyType); \myType.insert(ty); \}\va_end(args); \return myType; \}\
}; \
static AutoReg##CLASSNAME _regEditorCreator##CLASSNAME;	\
//通过static去实现实例化

RegMananger.cpp 

#include <map>
#include "RegMananger.h"struct RegMananger::Impl
{std::map<MyType, ICreator*> m_mapEditor;
};RegMananger& RegMananger::Getinstance()
{static RegMananger m_instance;return m_instance;
}RegMananger::RegMananger()
{m_pData = new Impl();
}RegMananger::~RegMananger()
{delete m_pData;
}void RegMananger::AddMananger(MyType type, ICreator* create)
{m_pData->m_mapEditor[type] = create;
}std::shared_ptr<BaseTool> RegMananger::GetEditor(MyType type)
{auto iter = m_pData->m_mapEditor.find(type);if (iter == m_pData->m_mapEditor.end()){return nullptr;}return iter->second->Create();
}

三：注册类

RegMananger.h

#pragma once
#include "Define.h"class RedColorTool:public BaseTool
{
public:RedColorTool() = default;~RedColorTool() = default;private:int data;
};

RegMananger.cpp 

#include "RedColor.h"
#include "RegMananger.h"REG_TOOL(RedColorTool, MyType::red, MyType::blue);

四：调用基类

BaseCmd.h

#pragma once
#include "RegMananger.h"class BaseCmd
{
public:BaseCmd() = default;virtual ~BaseCmd() = default;void SetType(MyType type) { m_type = type; };std::shared_ptr<BaseTool>  GetBaseTool(){return RegMananger::Getinstance().GetEditor(m_type);};protected:template<class _Tool, class _Ret, class ..._Arg>//_Ret:返回值，_Tool类名称，func：static函数，_Arg：函数传入参数_Ret InvokeTool(_Ret(_Tool::* func)(_Arg...), std::remove_cv_t<_Arg>... args){std::shared_ptr<_Tool> spEditor = std::dynamic_cast<_Tool*>(GetBaseTool());if (spEditor){if constexpr (std::is_same_v<_Ret,void>){(spEditor.get()->*func)(std::forward<_Arg>(args)...);}else{return (spEditor.get()->*func)(std::forward<_Arg>(args)...);}}else{std::cout << "class Error" << std::endl;}if constexpr (!std::is_same_v<_Ret, void>){return _Ret{};}}private:MyType m_type;
};

 五：普通类

#pragma once
#include "Define.h"
#include "RegMananger.h"class ColorTool :public BaseTool
{
public:ColorTool() =default;~ColorTool() = default;bool Create(int num,bool check);
private:};bool ColorTool::Create(int num, bool check)
{return true;
}REG_TOOL(ColorTool, MyType::red, MyType::blue);

六：继承调用类

#pragma once
#include "BaseCmd.h"
#include "ColorTool.h"class NewColorCmd:public BaseCmd
{
public:NewColorCmd() { SetType(MyType::red); };~NewColorCmd()=default;void Create();
private:};void NewColorCmd::Create()
{int num = 10;bool check = true;InvokeTool(&ColorTool::Create, num, check);
}