当我有两个对象时如何重载运算符<<？？（有关系）答案

【问题标题】：how to overload operator<< when i have two objects??(has a relationship)当我有两个对象时如何重载运算符<<？？（有关系）
【发布时间】：2017-05-28 23:55:13
【问题描述】：

我想额外显示对象的年龄，但我不知道如何在函数 ostream 中调用对象日期，因为它只需要两个参数。有什么建议？？我需要创建一个虚拟运算符并继承日期吗？

#ifndef HEARTRATE_H
#define HEARTRATE_H
#include <string>
#include <iostream>
#include "Date.h"

using std::string;
using std::cout;
using std::endl;

class HeartRate
{
public:
    HeartRate(string fn,string ln,Date d);
    string getfname();
    string getlname();
    Date getAge(Date& d);
    inline void printH(){
        cout<<Fname<<Lname<<date.getday()<<"/"<<date.getmonth()<<"/"<<date.getyear()<<"/"<<endl;
    }
    friend std::ostream&  operator<<(std::ostream& os,const HeartRate& hr){
        os<<"First name: "<<hr.Fname<<endl;
        os<<"Last name: "<<hr.Lname<<endl;
//I want to additional display the age of the object.
        os<<"The Date of birth is: "<<        
        return os;
    }
protected:
    string Fname;
    string Lname;
    Date date;
};

class Date
{
public:
    Date(int d,int m,int y);
    int getday(){return day;}
    int getmonth(){return month;}
    int getyear(){return year;}
    inline void print(){
        cout<<day<<"/"<<month<<"/"<<year;
    }
protected:
    int day;
    int month;
    int year;
};


#endif

【问题讨论】：

标签： c++ overloading operator-keyword ostream

【解决方案1】：

您还必须为类Date 重载插入运算符，以便能够将其用于该类的对象：

class Date
{
      public:
          friend ostream& operator << (ostream& out, const Date& theDate){
            out << theDate.day << " / " << theDate.month << " / " 
            << theDate.year;
              return out;
          }
      protected:
           int day;
           int month;
          int year;
  };

现在在你的班级HeartRate 你可以简单地写：

friend std::ostream&  operator<<(std::ostream& os,const HeartRate& hr){
    os<<"First name: "<<hr.Fname<<endl;
    os<<"Last name: "<<hr.Lname<<endl;
    //I want to additional display the age of the object.
    os << "The Date of birth is: "<<  hr.date;      
    return os;
}

【讨论】：