目录
一:日期类实现
二:const成员
三:取地址及const取地址操作符重载
一:日期类实现
//头文件#include <iostream>
using namespace std;class Date
{friend ostream& operator<<(ostream& out, const Date d);friend istream& operator>>(istream& in, const Date d);
public:Date(int year = 1900, int month = 1, int day = 1);void Print(){cout << "年 " << _year << "月 " << _month<<"日 " << _day << endl;}//得到对应年月的天数int GetMonthDay(int year, int month){static int day[13] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };if(month == 2 &&((year%100 != 0&& year%4==0) || (year % 400 == 0)))return day[month]+1;elsereturn day[month];}bool CheckDay();bool operator<(const Date d)const;bool operator<=(const Date d)const;bool operator==(const Date d)const;bool operator>=(const Date d)const;bool operator>(const Date d)const;bool operator!=(const Date d)const;Date& operator+=(int day);Date operator+(int day);Date& operator-=(int day);Date operator-(int day);Date operator++();Date operator++(int);Date operator--();Date operator--(int);int operator-(const Date d);private:int _year;int _month;int _day;
};ostream& operator<<(ostream& out, const Date d);
istream& operator>>(istream& in, const Date d);
//实现#include "Date.h"Date::Date(int year, int month, int day)
{_year = year;_month = month;_day = day;
}bool Date::CheckDay()
{if (_month > 12 || _month < 0 || _day <0 || _day > GetMonthDay(_year, _month))return false;elsereturn true;}bool Date::operator<(const Date d)const
{if (_year < d._year){return true;}else if (_year == d._year){if (_month < d._month)return true;else if (_month == d._month){return _day < d._day;}}return false;
}bool Date::operator<=(const Date d)const
{return ((*this) < d) || ((*this) == d);
}bool Date::operator==(const Date d)const
{return _year == d._year&& _month == d._month&& _day == d._day;}bool Date::operator>=(const Date d)const
{return ((*this) > d) || ((*this) == d);
}bool Date::operator>(const Date d)const
{return !((*this) <= d);
}bool Date::operator!=(const Date d)const
{return !((*this) == d);
}Date& Date::operator+=(int day)
{if (day < 0)return (*this) -= -day;_day += day;while (_day > GetMonthDay(_year, _month)){_day -= GetMonthDay(_year, _month);_month++;if (_month > 12){_year++;_month = 1;}}return (*this);
}
Date Date::operator+(int day)
{Date tmp = *this;tmp += day;return tmp;
}Date& Date::operator-=(int day)
{if (day < 0)return (*this) += -day;_day -= day;while (_day <= 0){if (_month-- < 1){_month = 12;_year--;}_day += GetMonthDay(_year, _month);}return (*this);
}
Date Date::operator-(int day)
{Date tmp = *this;tmp -= day;return tmp;
}Date Date::operator++()
{return (*this) += 1;
}
Date Date::operator++(int)
{Date tmp = *this;*this += 1;return tmp;
}Date Date::operator--()
{*this -= 1;return *this;
}
Date Date::operator--(int)
{Date tmp = *this;*this -= 1;return tmp;
}int Date::operator-(const Date d)
{int flag = 1;int n = 0;//假设d1 大, d2小Date d1 = *this;Date d2 = d;if (d1 < d2){flag = -1;d1 = d;d2 = *this;}while (d1 != d2){n++;d2++;}return n * flag;
}ostream& operator<<(ostream& out, const Date d)
{out << "年 " << d._year << "月 " << d._month << "日 " << d._day << endl;return out;
}istream& operator>>(istream& in, const Date d)
{cout << "请输入年月日->";in >> d._year >> d._month >> d._day;return in;
}
二:const成员
将 const 修饰的 “ 成员函数 ” 称之为 const 成员函数 , const 修饰类成员函数,实际修饰该成员函数
隐含的 this 指针 ,表明在该成员函数中 不能对类的任何成员进行修改。
class Date
{
public:Date(int year, int month, int day){_year = year;_month = month;_day = day;}//void Print(Date* const this) 本身指向的对象是不能修改的,但是指向的内容可以改 void Print(){cout << "年" << _year << endl;cout << "月" << _month << endl;cout << "日" << _day << endl;}//void Print(const Date* const this) 本身指向的对象 和 指向的对象的内容 都不可以修改void Print()const{cout << "年" << _year << endl;cout << "月" << _month << endl;cout << "日" << _day << endl;}private:int _year;int _month;int _day;
};int main()
{Date d1(2024, 4, 28);d1.Print();Date d2(2024, 4, 27);d2.Print();return 0;
}
三:取地址及const取地址操作符重载
这两个默认成员函数一般不用重新定义 ,编译器默认会生成。
class Date
{
public:Date* operator&(){return this;}const Date* operator&()const{return this;}
private:int _year;int _month;int _day;
};
这两个运算符一般不需要重载,使用编译器生成的默认取地址的重载即可,只有特殊情况,才需
要重载,比如 想让别人获取到指定的内容!