单例模式

#include <iostream>
using namespace std;

class Person
{
    private:
        string id;
        string hometown;
        static Person *ptr;
    public:
        static Person* create()
        {
            if(ptr == NULL)
            {
                ptr = new Person;
            }
            return ptr;
        }
};

Person* Person::ptr = NULL;

int main()
{
    Person *p = Person::create();
    system("pause");
    return 0;
}