C++ 根据对象名字创建对象

base.hpp的代码： 

#ifndef _H_DYNAMIC_H
#define _H_DYNAMIC_H

#include "Base.h"
#include <iostream>
#include <map>
using namespace std;

template<typename T> Base * createT() { return new T; }

struct BaseFactory {
    typedef std::map<std::string, Base*(*)()> map_type;

    static Base * createInstance(std::string const& s) {
        map_type::iterator it = getMap()->find(s);
        if(it == getMap()->end())
            return 0;
        return it->second();
    }

    protected:
    static map_type * getMap() {
        if(!map) { map = new map_type; } 
        return map; 
    }

    public:
    static map_type * map;
};

template<typename T>
struct DerivedRegister : BaseFactory { 
    DerivedRegister(std::string const& s) { 
        getMap()->insert(std::make_pair(s, &createT<T>));
        cout<<"add"<<endl;
    }
};
#define REGISTER_DEC_TYPE(NAME) static DerivedRegister<NAME> reg
#define REGISTER_DEF_TYPE(NAME) DerivedRegister<NAME> NAME::reg(#NAME)

#endif  

Base.h的代码：

#ifndef _H_BASE_H
#define _H_BASE_H
#include <iostream>
using namespace std;

class Base {
    string name;
public:
    virtual void print();
    virtual ~Base();
};

#endif

Base.cpp的代码： 

#include "Base.h"

Base::~Base(){
    cout<<"detructed"<<endl;
}

void Base::print(){
    cout<<"base"<<endl;

} 

derivedb.h的代码：

#include "derivedb.hpp"
DerivedRegister<DerivedB> DerivedB::reg("DerivedB");

void DerivedB::print(){
    cout<<"derived"<<endl;

} 

derivedb.hpp的代码：

#ifndef _H_DERIVEDB_H
#define _H_DERIVEDB_H

#include <iostream>
#include "base.hpp"
#include "Base.h"
using namespace std;

class DerivedB : public Base{
private:
    static DerivedRegister<DerivedB> reg;
public :
    void print();
};

#endif

main的测试代码：

#include "Animal.h"
#include "Cat.h"
#include <iostream>
#include "base.hpp"
#include <dlfcn.h>
#include "derivedb.hpp"
#include <map>
using namespace std;

BaseFactory::map_type * BaseFactory::map;
class Base;

void load(){
    void *handle = dlopen("./deriveb.so",RTLD_NOW|RTLD_GLOBAL);
    if(!handle)
    {
        std::cerr << dlerror() << std::endl;
        return;
    }
    else{
        cout<<"load OK"<<endl;
    }

    Base * bp = BaseFactory::createInstance("DerivedB");
    bp->print();
}

using namespace std;
int main(int argc, char ** argv ){
    load();
    return 0;

} 

编译：

g++ -fPIC -shared -o deriveb.so  derivedb.cpp  

g++ -c Base.cpp 

g++ -rdynamic -g -ldl  main.cpp Base.o

这里有一个非常关键的地方，就是这个-rdynamic，如果不加这个选项，dlopen会包undifined symbol，参考：http://stackoverflow.com/questions/480617/dlopen-issue