C++中的运算符重载

C++中类的运算符重载形式为：Object operator op(const Object&) const;

具体例子请看下面代码：

time.h

#ifndef TIME_H_
#define TIME_H_
#include "iostream"
using namespace std;

class Time{
private:
	int minute;
	int hour;

public:
	Time();
	Time(int h,int m);
	void AddHour(int h);
	void AddMin(int m);
	Time operator+(const Time& t) const;
	void show() const;
};
#endif

time.cpp

#include "time.h"

Time::Time()
{
	hour = minute = 0;
}

Time::Time(int h,int m)
{
	minute = m;
	hour = h;
}

void Time::AddHour(int h)
{
	//略去实现
}

void Time::AddMin(int m)
{
	//略去实现
}

Time Time::operator+(const Time& t) const
{
	Time sum;
	sum.minute = minute + t.minute;
	sum.hour = hour + t.hour + sum.minute/60;
	sum.minute = sum.minute%60;
	return sum;
}

void Time::show() const
{
	cout<<hour<<"hours,"<<minute<<"minutes"<<endl;
}

main.h

#include "time.h"

int main()
{
	Time planning;
	Time coding(2,40);
	Time fixing(5,55);
	Time total;
	cout<<"planning time:";
	planning.show();
	cout<<"coding time:";
	coding.show();
	cout<<"fixing time:";
	fixing.show();
	total = coding + fixing;
	cout<<"total time:";
	total.show();
	return 0;
}

运行结果为：

planning time:0hours,0minutes

coding time:2hours,40minutes

fixing time:5hours,55minutes

total time:8hours,35minutes

1. 重载后的运算符依然保持重载前的优先级

2. 不能重载这几种运算符 sizeof运算符、 . 成员运算符、.* 成员指针运算符、::作用域运算符、?:条件运算符

void show() const;

void Time::show() const

以这样的方式声明和定义的类函数被称为const成员函数，就像应尽可能将const引用和指针作为函数形参一样，只要类方法不修改调用对象，就应将其声明为const。