C++实现一个 Date （日期）类

---

Date.h

#pragma once

#include <iostream>
#include <assert.h>
using std::cout;
using std::endl;

class Date{
public:
	inline int GetMonthDay(int year, int month) const{
		static int monthArray[13] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
		if ((month == 2) 
			&& ((year % 4 == 0 && year % 100 != 0)|| (year % 400 == 0)))
		{
			return 29;
		}

		return monthArray[month];
	}

	Date(int year = 1900, int month = 1, int day = 1){
		if (year >= 1900
			&& month > 0 && month < 13
			&& day > 0 && day <= GetMonthDay(year, month))
		{
			_year = year;
			_month = month;
			_day = day;
		}
		else{
			//assert(false);
			cout << "非法日期" << endl;
		}
	}

	// d2(d1)
	Date(const Date& d){
		_year = d._year;
		_month = d._month;
		_day = d._day;
	}

	Date& Date::operator=(const Date& d){
		_year = d._year;              // this->_year = d._year;
		_month = d._month;
		_day = d._day;

		return *this;
	}

	void Print(){
		cout << _year << "-" << _month << "-" << _day << endl;
	}

	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++();		// 前置++
	Date operator++(int);	// 后置++

	Date& operator--();		// 前置--
	Date operator--(int);	// 后置--

	Date operator+(int day) const;
	Date operator-(int day) const;

	Date& operator+=(int day); 
	Date& operator-=(int day);

	int operator-(const Date&d) const;
private:
	int _year;
	int _month;
	int _day;
};

Date.cpp

#include "Date.h"

int Date::operator-(const Date&d) const{
	Date maxdate(*this);
	Date mindate(d);
	int flag = 1;
	if (*this < d){
		maxdate = d;
		mindate = *this;
		flag = -1;
	}

	int days = 0;
	while (mindate != maxdate){
		mindate += 1;
		++days;
	}

	return days * flag;
}

// ++d
Date& Date::operator++(){	// 前置++
	*this += 1;
	return *this;
}

// d++
Date Date::operator++(int){ // 后置++
	Date ret(*this);
	*this += 1;
	return ret;
}

//
Date& Date::operator--(){	// 前置--
	*this -= 1;
	return *this;
}

Date Date::operator--(int){ // 后置--
	Date tmp(*this);
	*this -= 1;

	return tmp;
}

Date Date::operator+(int day) const{
	Date ret = *this;
	ret += day;
	return ret;
}

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 == 13){
			++_year;
			_month = 1;
		}
	}

	return *this;
}

Date& Date::operator-=(int days){
	if (days < 0){
		return *this += -days;
	}

	_day -= days;
	while (_day <= 0){
		--_month;
		if (_month == 0){
			_month = 12;
			--_year;
		}
		_day += GetMonthDay(_year, _month);
	}
	return *this;
}

Date Date::operator-(int day) const{
	Date ret(*this);
	ret -= day;

	return ret;
}

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){
			if (_day > d._day){
				return true;
			}
		}
	}
	return false;
}

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);
}

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);
}