C++日期类的实现

前言：在类和对象比较熟悉的情况下，我们我们就可以开始制作日期表了，实现日期类所包含的知识点有构造函数，析构函数，函数重载，拷贝构造函数，运算符重载，const成员函数

1.日期类的加减运算

#define _CRT_SECURE_NO_WARNINGS 1
#include"data.h"
class Data
{
public://获取某年某月的天数int GetMonthday(int year, int month){int days[13] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };int day = days[month];if (month == 2){if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)){day += 1;}}return day;}Data(int year=1900,int month=1,int day=1){_year = year;_month = month;_day = day;}//拷贝构造//Data(const Data& d);//日期赋值Data& operator = (const Data & d) const{_year = d._year;_month = d._month;_day = d._day;return *this;}Data& operator-=(int day){_day -= day;while (_day <= 0){if (_month == 1){_year--;_month = 12;}else{_month--;}_day = GetMonthday(_year, _month) + _day;}return *this;}Data& operator+=(int day){_day += day;while (_day > GetMonthday(_year, _month)){_day = _day - GetMonthday(_year, _month);_month++;if (_month == 13){_year++;_month = 1;}}return *this;}void Print(const Data& d){cout << _year << "年" << _month << "月" << _day << "日" << endl;}private:int _year;int _month;int _day;};int main()
{Data d1(2023,12,31);Data d2(d1);d2 = d2.operator+=(10000);d2.Print(d2);return 0;
}

2 日期类的运算符重载

类里面有默认的拷贝构造函数（不显含），还有默认的构造函数（不显含），你也可以把这个默认的构造函数写出来，只是不显含的构造函数对类里面的内置类型不做处理，自定义类型会调用它的构造函数，就会处理一下。

//日期赋值
Data& operator = (const Data & d)
{_year = d._year;_month = d._month;_day = d._day;return *this;
}Data& operator-=(int day)
{_day -= day;while (_day <= 0){if (_month == 1){_year--;_month = 12;}else{_month--;}_day = GetMonthday(_year, _month) + _day;}return *this;
}Data& operator+=(int day)
{_day += day;while (_day > GetMonthday(_year, _month)){_day = _day - GetMonthday(_year, _month);_month++;if (_month == 13){_year++;_month = 1;}}return *this;
}Data& operator++()//前置++
{_day++;if (_day > GetMonthday(_year, _month)){_day = _day - GetMonthday(_year, _month);_month++;if (_month == 13){_year++;_month = 1;}}return *this;
}Data& operator++(int)//后置++
{Data d = *this;++_day;return d;
}//运算符重载，比较两个日期的大小
bool operator>(const Data& d)
{return ((_year > d._year) || (_year==d._year&&_month > d._month) || (_year == d._year && _month == d._month&&_day > d._day));
}bool operator>=(const Data& d)
{return !((_year < d._year) || (_year == d._year && _month < d._month) || (_year == d._year && _month == d._month && _day < d._day));
}bool operator<(const Data& d)
{return ((_year < d._year) || (_year == d._year && _month < d._month) || (_year == d._year && _month == d._month && _day < d._day));
}bool operator<=(const Data& d)
{return !((_year > d._year) || (_year > d._year && _month > d._month) || (_year == d._year && _month == d._month && _day > d._day));}bool operator!=(const Data& d)
{return !((_year == d._year) && (_month == d._month) && (_day == d._day));
}int operator-(Data& d)
{Data max = *this;Data min = d;int flag = 1;if (*this < d){max = d;min = *this;flag = -1;}int n = 0;while (min != max){++min;++n;}return flag * n;
}

3 我们将运算符重载的函数和两个日期相差的天数进行配合计算

int operator-(Data& d)
{Data max = *this;Data min = d;int flag = 1;if (*this < d){max = d;min = *this;flag = -1;}int n = 0;while (min != max){++min;++n;}return flag * n;
}

int main()
{Data d1(2023,12,31);//Data d2(d1);Data d2(1900,11,30);//d2 = d2.operator+=(10000);d2.Print(d2);cout << d2.operator-(d1) << endl;return 0;
}

所有源码的实现如下

data.h#pragma once
#include<iostream>
using namespace std;
class Data
{
public://获取某年某月的天数int GetMonthday(int year, int month){int days[13] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };int day = days[month];if (month == 2){if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)){day += 1;}}return day;}Data(int year = 1900, int month = 1, int day = 1){_year = year;_month = month;_day = day;}//拷贝构造//Data(const Data& d);//日期赋值Data& operator = (const Data& d);Data& operator-=(int day);Data& operator+=(int day);Data& operator++();//前置++Data& operator++(int);//后置++//运算符重载，比较两个日期的大小bool operator>(const Data& d);bool operator>=(const Data& d);bool operator<(const Data& d);bool operator<=(const Data& d);bool operator!=(const Data& d);int operator-(Data& d);void Print(const Data& d);private:int _year;int _month;int _day;};data.cpp#define _CRT_SECURE_NO_WARNINGS 1
#include"data.h"
Data& Data::operator = (const Data& d)
{_year = d._year;_month = d._month;_day = d._day;return *this;
}Data& Data::operator-=(int day)
{_day -= day;while (_day <= 0){if (_month == 1){_year--;_month = 12;}else{_month--;}_day = GetMonthday(_year, _month) + _day;}return *this;
}Data& Data::operator+=(int day)
{_day += day;while (_day > GetMonthday(_year, _month)){_day = _day - GetMonthday(_year, _month);_month++;if (_month == 13){_year++;_month = 1;}}return *this;
}Data& Data::operator++()//前置++
{_day++;if (_day > GetMonthday(_year, _month)){_day = _day - GetMonthday(_year, _month);_month++;if (_month == 13){_year++;_month = 1;}}return *this;
}Data& Data::operator++(int)//后置++
{Data d = *this;++_day;return d;
}//运算符重载，比较两个日期的大小
bool Data::operator>(const Data& d)
{return ((_year > d._year) || (_year == d._year && _month > d._month) || (_year == d._year && _month == d._month && _day > d._day));
}bool Data::operator>=(const Data& d)
{return !((_year < d._year) || (_year == d._year && _month < d._month) || (_year == d._year && _month == d._month && _day < d._day));
}bool Data::operator<(const Data& d)
{return ((_year < d._year) || (_year == d._year && _month < d._month) || (_year == d._year && _month == d._month && _day < d._day));
}bool Data::operator<=(const Data& d)
{return !((_year > d._year) || (_year > d._year && _month > d._month) || (_year == d._year && _month == d._month && _day > d._day));}bool Data::operator!=(const Data& d)
{return !((_year == d._year) && (_month == d._month) && (_day == d._day));
}int Data::operator-(Data& d)
{Data max = *this;Data min = d;int flag = 1;if (*this < d){max = d;min = *this;flag = -1;}int n = 0;while (min != max){++min;++n;}return flag * n;
}void Data::Print(const Data& d)
{cout << _year << "年" << _month << "月" << _day << "日" << endl;
}int main()
{Data d1(2023,12,31);//Data d2(d1);Data d2(1900,11,30);//d2 = d2.operator+=(10000);d2.Print(d2);cout << d2.operator-(d1) << endl;return 0;
}