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目录
头文件
函数实现
前言
? hello! 各位铁子们大家好哇。
今日更新了类与对象日期计算器的内容
? 欢迎大家关注?点赞?收藏⭐️留言?
头文件
#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);//++d1Date& 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);声明流插入<<和流提取>>时，应在类外面声明，不然this指针会占据第一个形参，Date就只能是左操作数了，打印时就会变成d1<<cout; ，不符合常规写法。在类外面声明时，为了不把private打开，可以进行友元声明，就可以在不打开private的情况下，访问private。
函数实现
#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;}上方实现时，有日期+天数和日期+=天数。二者实现其中一个即可复用另一个。但是要先实现哪一个更好呢？
