困难与类的实例，从常量字符串

K时，我这里有一个基类和众多的派生类。下面的基类，在同一文件中，我有一对夫妇登记在地图对象派生的对象std :: string的指标，负责对象，然后将实例化的对象，给予有效的字符串索引的对象。注册一个类的对象，我宣布的类型DerivedRegister的对象在派生类的私有成员，一个类的模板参数，然后调用它的外部类的构造函数。够简单吧？错了。因为对象的方式成立，并宣布，我把语法错误时，调整的基类sligthly。在这里我的base.h是:

#ifndef BASE_H

#define BASE_H

 

#include <map>

#include <string>

#include <fstream>

using namespace std;

 

class base{

    #define DECLARE_ENTITY(T) static DerivedRegister<T> reg;

    #define LINK_ENTITY(T, name) DerivedRegister<T> T::reg(name);

public:

    int getMeh() {return m_meh;}

    virtual void GetParams(fstream & stream);

protected:

    int m_meh;

    string m_EntityName;

};

 

template<class T> base * createT() {return new T;}

class BaseFactory{

public:

    typedef map<string, base *(*)()> map_type;

 

    static base * createInstance(const string & s) {

        if ( !getMap()->count(s) )

            return NULL;

        map_type::iterator it = getMap()->find(s);

        return it->second();

    }

 

protected:

 

    static map_type * getMap() {

        if(!m_Map) {m_Map = new map_type;}

        return m_Map;

    }

 

private:

    static map_type * m_Map;

};

 

template<class T>

class DerivedRegister : BaseFactory {

public:

    DerivedRegister(std::string const & s)

    {

        getMap()-> insert( pair<string, base*(*)()> (s, &createT<T>));

    }

};

 

BaseFactory::map_type * BaseFactory::m_Map = new map_type();

 

#endif

#include <iostream>

#include <vector>

using namespace std;

#include "base.h"

#include "derived.h"

#include "second.h"

#include "third.h"

#include "fourth.h"



int main()

{

    BaseFactory yosh;

    vector<base *> meh;

 

    for(int i = 0; i < 20; i++)

    {

        if(i % 4 == 0)

            meh.push_back(yosh.createInstance("derived"));

        else if( i % 4 == 1)

            meh.push_back(yosh.createInstance("second"));

        else if( i % 4 == 2)

            meh.push_back(yosh.createInstance("third"));

        else

            meh.push_back(yosh.createInstance("fourth"));

    }

 

    for(int i = 0; i < (int) meh.size(); i++)

    {

        if(meh[i])

            cout << meh[i]->getMeh() << "\n";

        else

            cout << "invalid\n";

    }

 

    for(int i = 0; i < (int) meh.size(); i++)

    {

        if(meh[i]) delete meh[i];

    }

    return 0;

}