C++ Integer ++运算符重载

一、整体代码

      Integer.h

#ifndef _INTEGER_H_
#define _INTEGER_H_
class Integer
{
public:
    Integer(int n);
    ~Integer();
    Integer(const Integer& other);//拷贝构造函数
    Integer& operator++();
    //friend Integer& operator++(Integer& i);
    Integer operator++(int n);
    //friend Integer operator++(Integer& i, int n);
    void Display() const;
private:
    int n_;
};
#endif // _INTEGER_H_

      Integer.cpp

#include"Integer.h"
#include<iostream>
usingnamespace std;
Integer::Integer(int n) : n_(n)
{
}
Integer::~Integer()
{
}

Integer::Integer(const Integer& other) : n_(other.n_)

{

  //num_ = other.num_;  

  cout<<"Initializing with other "<<n_<<endl;

}

Integer& Integer::operator++()
{
//cout<<"Integer& Integer::operator ++()"<<endl;
++n_;
return*this;//返回自身引用
}
//Integer& operator++(Integer& i)
//{
//    cout<<"Integer& operator++(Integer& i)"<<endl;
//    ++i.n_;
//    return i;
//}
Integer Integer::operator++(int n)
{
//cout<<"Integer& Integer::operator ++()"<<endl;
//n_++;
   Integer tmp(n_);
   n_++;
return tmp;
}
//Integer operator++(Integer& i, int n)
//{
//    Integer tmp(i.n_);
//    i.n_++;
//    return tmp;
//}
void Integer::Display() const
{
   cout<<n_<<endl;
}

     01.cpp

#include "Integer.h"
#include <iostream>
using namespace std;
int main(void)
{
    Integer n(100);
    n.Display();//显示100
    Integer n2 = ++n;//Integer n2 = n.operator++();把自身调用返回，赋给n2，调用了一次拷贝构造函数,Initializing with other 101
                    
    n.Display();//101
    n2.Display();//101
    Integer n3 = n++;//Integer n3 = n.operator++(int n);把原来临时的对象（n_为101）由n3接管，不调用拷贝构造函数
    n.Display();//102
    n3.Display();//101
    return 0;
}

二、解释

      如果只是调用++n;再调用n.Display();也显示101。