引用成员变量 和 类对象做成员变量

#include <iostream>
using namespace std;

class Date
{
    int month, year;
public:
    Date(int m, int y):month(m), year(y){};
};

class Person_ref
{
    Date &birth;
    string name;
public:
    Person_ref::Person_ref(Date &b, string n): name(n), birth(b){};
    Date *GetBirth(){return &birth;}
    Date &GetBirth_(){return birth;}
};

class Person_obj
{
    Date birth;
    string name;
public:
    Person_obj::Person_obj(Date b, string n): name(n), birth(b){};
    Date *GetBirth(){return &birth;}
    Date &GetBirth_(){return birth;}
};

int main()
{
    Date date1(4, 1989), date2(5, 1990);
    Person_ref person_ref(date1, "Elva");        //person.birth字段成为为date1这段空间的别名
    Person_obj person_obj(date1, "Elva");        //为person_obj.birth字段重辟一段空间，然后拿date1的值对这段空间进行值赋值

    Date *pd = person_ref.GetBirth();
    Date newDate = person_ref.GetBirth_();       //为newDate重辟一段空间，然后取person_ref.birth中数据对其进行值赋值
    Date &refDate = person_ref.GetBirth_();      //refdate成为person_ref.birth, date1这段空间的新别称

    cout << "date1:           " << &date1 <<endl;
    cout << "person_ref.birth:" << person_ref.GetBirth()<<endl;
    cout << "person_obj.birth:" << person_obj.GetBirth()<<endl;
    cout << "refDate:         " << &refDate <<endl;
    cout << "tmpDate:         " << &newDate <<endl;

    refDate = date2;                             //对date1,person_ref.birth,refDate这段空间进行"值"赋值
    cout << "refDate after revalue:  " << &refDate <<endl;

    return 1;
}