看了MFC中的動態(tài)創(chuàng)建對象后，感覺動態(tài)創(chuàng)建對象算是一種技術(shù)吧，理論上說算是一種設(shè)計(jì)模式，

C++ 類工廠實(shí)現(xiàn)動態(tài)對象創(chuàng)建

。其實(shí)創(chuàng)建的原理很明了，把對象的類別名稱和其構(gòu)造函數(shù)用容器記錄下來，在需要的時(shí)候給出創(chuàng)建類別查找容器即可創(chuàng)建對象。當(dāng)然這里我們需要自定義一個(gè)全局的函數(shù)指針用來指向類別的構(gòu)造函數(shù)。在這里我們使用類工廠模式，在淚工廠中我們定義一個(gè)通用構(gòu)造函數(shù)，將函數(shù)指針指向它。下面是參考一位網(wǎng)友思路來整理和摸索的代碼：

    //通用的函數(shù)指針

    typedef void *(*CREATE_FUNC)();

    //創(chuàng)建類的工廠類

   

class DynObjectFactory{public:    static void *CreateObject( const string &name)    {        map<string, CREATE_FUNC>::const_iterator it;        it = mapCls_.find(name);        if (it == mapCls_.end())            return  0;        else            return it->second();  //func();    }    static void Register( const string &name, CREATE_FUNC func)    {        mapCls_[name] = func;    }private:    static map<string, CREATE_FUNC> mapCls_;};//頭文件被包含多次，也只定義一次mapCls_;__declspec(selectany) map<string, CREATE_FUNC> DynObjectFactory::mapCls_;class Register{public:    Register( const string &name, CREATE_FUNC func)    {        DynObjectFactory::Register(name, func);    }};

    #define REGISTER_CLASS(class_name) \

    class class_name##Register { \

    public: \

    static void* NewInstance() \

    { return new class_name; } \

    private: \

    static Register reg_; \

    }; \

    Register class_name##Register::reg_(#class_name, class_name##Register::NewInstance)

    //CircleRegister

    //下面是測試類 *.h

    class Shape

    {

    public:

    virtual void Draw() = 0;

    virtual ~Shape() {}

    };

    class Circle : public Shape

    {

    public:

    void Draw();

    ~Circle();

    };

    class Square : public Shape

    {

    public:

    void Draw();

    ~Square();

    };

    class Rectangle : public Shape

    {

    public:

    void Draw();

    ~Rectangle();

    };

    //*.cpp

    void Circle::Draw()

    {

    cout << "Circle::Draw() ..." << endl;

    }

    Circle::~Circle()

    {

    cout << "~Circle ..." << endl;

    }

    void Square::Draw()

    {

    cout << "Square::Draw() ..." << endl;

    }

    Square::~Square()

    {

    cout << "~Square ..." << endl;

    }

    void Rectangle::Draw()

    {

    cout << "Rectangle::Draw() ..." << endl;

    }

    Rectangle::~Rectangle()

    {

    cout << "~Rectangle ..." << endl;

    }

    REGISTER_CLASS(Circle);

    REGISTER_CLASS(Square);

    REGISTER_CLASS(Rectangle);

    //main.cpp

    void DrawAllShapes( const vector &v)

    {

    vector::const_iterator it;

    for (it = v.begin(); it != v.end(); ++it)

    {

    (*it)->Draw();

    }

    }

    void DeleteAllShapes( const vector &v)

    {

    vector::const_iterator it;

    for (it = v.begin(); it != v.end(); ++it)

    {

    delete(*it);

    }

    }

    int main( void)

    {

    vector v;

    Shape *ps;

    ps = static_cast(DynObjectFactory::CreateObject( "Circle"));

    v.push_back(ps);

    ps = static_cast(DynObjectFactory::CreateObject( "Square"));

    v.push_back(ps);

    ps = static_cast(DynObjectFactory::CreateObject( "Rectangle"));

    v.push_back(ps);

    DrawAllShapes(v);

    DeleteAllShapes(v);

    return 0;

    }