C++ 工厂方法2

#include <iostream>#include <map>#include <string>class DeviceBase;typedef DeviceBase* (*FactoryFunction)();class DeviceFactory{public:static void Register(std::string name, FactoryFunction instanceFunction){    m_FactoryFunctions[name] = instanceFunction;}static DeviceBase* GetInstance(std::string name){     if (m_FactoryFunctions.count(name))    {        return m_FactoryFunctions[name]();    }    else    {        return NULL;     }}private:    static std::map<std::string, FactoryFunction> m_FactoryFunctions;};std::map<std::string, FactoryFunction> DeviceFactory::m_FactoryFunctions;class DeviceBase{public:    virtual void Draw() = 0;};class Circle : public DeviceBase{public:    void Draw()     {         std::cout << "Drawing a Circle......Done" << std::endl;     }    static DeviceBase* CreateInstance()     {        return new Circle;    }};class Triangle : public DeviceBase{public:void Draw() {     std::cout << "Drawing a Triangle......Done" << std::endl; }static DeviceBase* CreateInstance() {    return new Triangle;}};// 工厂模式中的单例模式class TSingleton : public DeviceBase{public:void Draw() {     std::cout << "Test Singleton......Done" << std::endl; }static DeviceBase* CreateInstance() {    static TSingleton* _instance = new TSingleton;    return _instance;}};int main(){DeviceFactory::Register("circle", &Circle::CreateInstance);DeviceFactory::Register("triangle", &Triangle::CreateInstance);DeviceFactory::Register("singleton", &TSingleton::CreateInstance);DeviceBase* pShape = NULL;pShape = DeviceFactory::GetInstance("singleton");if (NULL == pShape){    std::cout << "Can't find the produce in the factory!" << std::endl;}else{    pShape->Draw();    delete pShape;    pShape = NULL;}return 0;}