【C++】类与对象（日期计算器）

#include<iostream>
#include<assert.h>
using namespace std;

class Date
{
public:
	bool CheckInvalid() const;
	Date(int year = 1, int month = 1, int day = 1);
	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) const;

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

	//++d1
	Date& operator++();

	//为了跟前置++区分，强行增加一个int形参，构成重载区分
	//d1++
	Date operator++(int);

	//日期-日期
	int operator-(const Date& d) const;

	//如果不声明和定义分离，本质就是内联
	int GetMonthDay(int year, int month) const
	{
		assert(month > 0 && month < 13);
		static int monthDays[13] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };  //因为要经常调用，所以可以设为静态的
		if ( month == 2&&((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) )
		{
			return 29;
		}

		return monthDays[month];
	}

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

	//void operator<<(ostream& out)
	//{
	//	out << _year << "年" << _month << "月" << _day << "日" << endl;
	//}

	//友元声明
	friend ostream& operator<<(ostream& out, const Date& d);
	friend istream& operator>>(istream& in, Date& d);

private:
	int _year;
	int _month;
	int _day;
};

ostream& operator<<(ostream& out, const Date& d);
istream& operator>>(istream& in,  Date& d);

#include"Date.h"

Date::Date(int year , int month, int day )
{
	_year = year;
	_month = month;
	_day = day;

	if (!CheckInvalid())
	{
		cout << "构造日期非法" << endl;
	}
}

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);
}

Date& Date::operator+=(int day)
{
	_day += day;
	while (_day > GetMonthDay(_year, _month))
	{
		_day -= GetMonthDay(_year, _month);
		++_month;
		if (_month == 13)
		{
			++_year;
			_month = 1;
		}
	}
	return *this;//可以用引用返回，出了作用域还在
}

Date Date::operator+(int day) const
{
	//Date tmp(*this);
	Date tmp = *this;  //拷贝构造
	tmp += day;

	return tmp;
}



//Date Date::operator+(int day)
//{
//	//Date tmp(*this);
//	Date tmp = *this;  //拷贝构造
//
//	tmp._day += day;
//	while (tmp._day > GetMonthDay(tmp._year, tmp._month)) 
//	{
//		tmp._day -= GetMonthDay(tmp._year, tmp._month); 
//		++tmp._month; 
//		if (tmp._month == 13) 
//		{ 
//			++tmp._year; 
//			tmp._month = 1; 
//		}
//	}
//	return tmp;  //不能用引用返回，因为他是局部对象，出了作用域就不在了
//}
//
//
//Date& Date::operator+=(int day)
//{
//	*this = *this + day;
//	return *this;
//}

Date Date::operator-(int day) const
{
	Date tmp = *this;
	tmp -= day;
	return tmp;
}

Date& Date::operator-=(int day)
{
	_day -= day;
	while(_day < 0)
	{
		--_month;
		if (_month == 0)
		{
			--_year;
			_month = 12;
		}
		_day += GetMonthDay(_year, _month);
	}
	return *this;
}

//++d  ->d.operator++()  编译器自动转换
Date& Date::operator++()
{
	*this += 1;
	return *this;
}

//d++  ->d.operator(0)   C++规定：后置++重载时多增加一个int类型的参数，但调用函数时该参数不用传递，编译器自动传递
Date Date::operator++(int)  //规定只能是int，形参名字可以不写
{
	Date tmp = *this;
	*this += 1;
	return tmp;
}

int Date::operator-(const Date& d) const
{
	int flag = 1;
	Date max = *this;
	Date min = d;

	if (*this < d)
	{
		int flag = -1;
		max = d;
		min = *this;
	}

	int n = 0;
	while (min != max)
	{
		++min;
		++n;
	}
	return n * flag;
}

bool Date::CheckInvalid() const
{
	if (_year <= 0
		|| _month < 1 || _month>12
		|| _day<1 || _day>GetMonthDay(_year, _month))
	{
		return false;
	}
	else
	{
		return true;
	}
}

ostream& operator<<(ostream& out, const Date& d)
{
	out << d._year << "年" << d._month << "月" << d._day << "日" << endl;
	return out;
}

istream& operator>>(istream& in, Date& d)
{
	while (1)
	{
		cout << "请输入年月日:" << endl;
		in >> d._year >> d._month >> d._day;

		if (!d.CheckInvalid())
		{
			cout << "输入了无效日期，请重新输入" << endl;
		}
		else
		{
			break;
		}	
	}
	return in;
}