C++设计模式-singleton单例模式_new

class nocopyable
{
protected:
nocopyable(){};
virtual ~nocopyable(){};
nocopyable(const nocopyable&);
nocopyable& operator = (const nocopyable&);
};

    template <typename T>
    class singleton : public nocopyable
    {
    public:
        static T* instance()
        {
            if (m_instance == NULL) {
                m_instance = new T();
            }
            return m_instance;
        }

        static T * get_instance()
        {
            if (m_instance == NULL) {
                printf("m_instance is NULL\n");
            }
            return m_instance;
        }

        static void destory_instance()
        {
            if (m_instance != NULL) {
                delete m_instance;
                m_instance = NULL;
            }
        }

    private:
        static T *m_instance;
    };

    template<typename T>
    T* singleton<T>::m_instance = NULL;

class MySingletonClass : public singleton<MySingletonClass> {
public:
    MySingletonClass() {}
    ~MySingletonClass() {}

public:
    void DoPrint() {
        printf("This is MySingletonClass.\n");
    }
};

int main()
{
    MySingletonClass::instance();
    MySingletonClass::get_instance()->DoPrint();
    MySingletonClass::destory_instance();

    getchar();
    ;
}