C++反射类和成员函数的实现

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最新推荐文章于 2025-07-12 21:26:08 发布

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本文介绍了一种在C++中实现反射机制的方法，通过定义工厂类和基类来管理类实例的创建及成员函数的调用。利用STL标准模板库实现了类注册、实例化和成员函数反射。

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原文地址：http://blog.wangziliang.com/2012/12/28/c%E5%8F%8D%E5%B0%84%E5%87%BD%E6%95%B0%E5%92%8C%E7%B1%BB%E7%9A%84%E5%AE%9E%E7%8E%B0/

C++反射类和成员函数的实现，需要用到STL标准模板库

//定义反射工厂类以及基类NSObject
#ifndef __NS_OBJECT_FACTORYE_H__
#define __NS_OBJECT_FACTORYE_H__
 
#include <map>
#include <string>
 
 
typedef void* (*SEL)(void);
typedef SEL (*callFuc)(void);
 
class NSObject{
public:
    Base(){};
    ~Base(){};
};
 
struct NSObjectFactory {
 
    typedef std::map<std::string, NSObject*(*)()> map_type;
    typedef std::map<std::string, callFuc> fuc_map_type;
 
private:
 
    static map_type * m_map;
    static fuc_map_type * fuc_map;
 
protected:
 
public:
 
    static NSObject * createInstance(std::string const& s){
        map_type::iterator it = getMap()->find(s);
        if(it == getMap()->end())
            return 0;
        return it->second();
    }
  
    static SEL callFaction(std::string const& s) {
        fuc_map_type::iterator it = getFunctionMap()->find(s);
        if(it == getFunctionMap()->end())
            return 0;
        return it->second();
  
    }
 
    static map_type * getMap(){
        // never delete'ed. (exist until program termination)
        // because we can't guarantee correct destruction order 
        if(!m_map) { m_map = new map_type; } 
        return m_map;
    }
 
    static fuc_map_type* getFunctionMap() {
  
        if(!fuc_map) { fuc_map = new fuc_map_type(); } 
  
        return fuc_map; 
  
    }
     
};
 
NSObjectFactory::map_type * NSObjectFactory::m_map = 0;
 
NSObjectFactory::fuc_map_type * NSObjectFactory::fuc_map = 0;
 
template<typename T> NSObject * createT() { return (NSObject *)(new T); }
 
 
template<typename T>
struct NSObjectRegister : NSObjectFactory { 
    NSObjectRegister(std::string const& s) { 
        getMap()->insert(std::make_pair(s, &createT<T>));
    }
};
 
#define REFECTION_CLASS_IMPLEMENT_DEFINE(NAME) \
    virtual string toString(){return #NAME;}; \
    static NSObjectRegister<NAME> registerNSObject
 
#define REFECTION_CLASS_IMPLEMENT(NAME) \
    NSObjectRegister<NAME> NAME::registerNSObject(#NAME)
 
#define NSClassFromString(NAME) \
    NSObjectFactory::createInstance(NAME)
 
struct FuctionRegister : NSObjectFactory { 
    FuctionRegister(std::string const& s, callFuc f) { 
        getFunctionMap()->insert(std::make_pair(s, f));
    }
  
};
  
#define REFECTION_FUNCTION_IMPLEMENT(NAME) \
    static FuctionRegister* f_reg_##NAME = new FuctionRegister(#NAME, (callFuc)NAME)
 
#define NSSelectorFromString(NAME) \
    NSObjectFactory::callFaction(NAME)
 
#endif // __NS_OBJECT_FACTORYE_H__

//===============================================

//示例封装成员函数反射方法定义一个base类
#define __EJ_GET_POINTER_TO(NAME) \
    SEL _ptr_to_##NAME() { \
        return (SEL)NAME; \
    } \
    REFECTION_FUNCTION_IMPLEMENT(_ptr_to_##NAME);
 
#define EJ_BIND_FUNCTION_DEFINE(NAME, ARGC_NAME, ARGV_NAME) \
    int _func_##NAME(size_t ARGC_NAME, const char* ARGV_NAME)
 
#define EJ_BIND_FUNCTION(CLASS, NAME, ARGC_NAME, ARGV_NAME) \
    \
    static int _##CLASS##_func_##NAME( \
        Base* object, \
        size_t argc, \
        const char argv[] \
    ) { \
        CLASS* instance = (CLASS*)object; \
        int ret = instance->_func_##NAME(argc, argv); \
        return ret; \
    } \
    __EJ_GET_POINTER_TO(_##CLASS##_func_##NAME)\
    \
    /* The actual implementation for this method */ \
    int CLASS::_func_##NAME(size_t ARGC_NAME, const char* ARGV_NAME)
 
class Base: public NSObject {
public:
    Base();
    ~Base();
    REFECTION_CLASS_IMPLEMENT_DEFINE(Base);//反射类申明
 
    EJ_BIND_FUNCTION(EJBindingEjectaCore,include, argc, argv )//反射成员函数申明
};
 
REFECTION_CLASS_IMPLEMENT(Base);//反射类实现
 
//反射成员函数类申明
EJ_BIND_FUNCTION(EJBindingEjectaCore,include, argc, argv ) {
    if( argc < 1 ) { return -1; }
    return 1;
}

//===========================================

//使用方法
typedef int (*CALL_BACK)( Base* object,  size_t argc,  const char argv[] );
 
int main(){
  
    NSObject* object = NSClassFromString("Base");//获得反射对象
    SEL callback = NSSelectorFromString("_ptr_to__Base_func_include");//获得函数指针
    ((CALL_BACK)callback)((Base*)object, 0, NULL);//调用静态函数使其调用object对象的成员函数
    return 0;
  
}