默认成员函数的练习之实现日期类

实现日期类

// Date.h
#define  _CRT_SECURE_NO_WARNINGS 1
#pragma once
#include<iostream>
#include<assert.h>using namespace std;class Date
{
public://构造函数Date(int year = 1, int month = 1, int day = 1);// 因为日期类没有涉及资源开销，所以不需要写拷贝构造和析构函数//打印void Print();// 赋值重载Date& operator=(const Date& d);//操作符重载bool operator<(const Date& d);bool operator<=(const Date& d);bool operator>(const Date& d);bool operator>=(const Date& d);bool operator==(const Date& d);bool operator!=(const Date& d);//查找每个月的天数,直接定义在类中，默认其是内联函数（因为要多次调用）int GetMonthDay(int year, int month){assert(month > 0 && month < 13);//用static修饰，固定在静态区，避免每次调用函数都创建一个数组static int monthDayArray[13] = { -1, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; if (month == 2 && ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)){ // 考虑闰年的情况，并且细节的是先判断是不是二月return 29;}elsereturn monthDayArray[month];}//日期加等整数Date& operator+=(int day);//日期加整数Date operator+(int day);//日期减等整数Date& operator-=(int day);//日期减整数Date operator-(int day);//日期前置++Date& operator++();//日期后置++Date operator++(int); //日期前置--Date& operator--();//日期后置--Date operator--(int);//日期减日期int operator-(const Date& d);private:int _year;int _month;int _day;
};

// Date.cpp
#define  _CRT_SECURE_NO_WARNINGS 1
#include"Date.h"Date::Date(int year, int month, int day) // 1.要加上访问限定符 2. 声明写缺省值，实现不写
{_year = year;_month = month;_day = day;
}void Date::Print()
{cout << _year << "/" << _month << "/" << _day << endl;
}Date& Date::operator=(const Date& d)// 1.加上返回值，可实现连续赋值 2.使用引用传参减少拷贝构造函数的调用
{if (this != &d) // 防止出现自己给自己赋值的情况{_year = d._year;_month = d._month;_day = d._day;}return *this;
}bool Date::operator<(const Date& d)
{if (_year < d._year){return true;}else if (_year == d._year&& _month < d._month){return true;}else if (_year == d._year&& _month == d._month&& _day < d._day){return true;}return false;
}bool Date::operator==(const Date& d)
{return _year == d._year&& _month == d._month&& _day == d._day;
}bool Date::operator<=(const Date& d)
{return *this < d || *this == d; // 函数复用，减少代码冗余
}bool Date::operator>(const Date& d)
{return !(*this <= d);
}bool Date::operator>=(const Date& d)
{return !(*this < d);
}bool Date::operator!=(const Date& d)
{return !(*this == d);
}Date& Date::operator+=(int day)
{if (day < 0){return *this -= -day; // 传入的日期为负数，复用-=（下面实现）}_day += day;while (_day > GetMonthDay(_year, _month)){_day -= GetMonthDay(_year, _month);_month++;if (_month == 13){_year++;_month = 1;}}return *this; // 返回增加day天数后的日期
}Date Date::operator+(int day) // 这里就不可以用引用做返回值了，原因是tmp出了函数作用域就被销毁
{Date tmp = *this; // 拷贝构造return tmp += day;
}Date& Date::operator-=(int day)
{if (day < 0){return *this += -day;}_day -= day;while (_day < 0){_month--;if (_month == 0){_year--;_month = 12;}_day += GetMonthDay(_year, _month); // 这个要放在后面}return *this;
}Date Date::operator-(int day)
{Date tmp = *this;return tmp -= day;
}Date& Date::operator++()
{return *this += 1;
}Date Date::operator++(int) // 参数的目的是构成函数重载
{Date tmp = *this;*this += 1;return tmp; // 注意返回值
}Date& Date::operator--()
{return *this -= 1;
}Date Date::operator--(int)
{Date tmp = *this;*this -= 1;return tmp; 
}int Date::operator-(const Date& d)
{//假设一个大的Date max = *this;Date min = d;int flag = 1;if (*this < d) // 说明假设错误{max = d;min = *this;flag = -1;}int n = 0;while (min != max){++min;++n;}return n * flag;
}

//test.cpp
#define  _CRT_SECURE_NO_WARNINGS 1
#include"Date.h"int main()
{Date d1(2024, 9, 27);d1.Print();Date d2 = d1; // 使用默认的拷贝构造//Date d2(d1);d2.Print();Date d3(2024, 9, 28);//d3 = d1; // 测试赋值重载//d3.Print();Date d4(2024, 9, 30);d4 = d3 = d1; // 连续赋值d4.Print();bool ret = d3 > d4;cout << ret << endl; // 0Date d5(2024, 10, 1);Date ret2 = d5 -= 100;ret2.Print(); // 2024/6/23Date year(2025, 1, 29);int ret3 = d3 - year;cout << ret3 << endl;Date birth(2005, 8, 23); // 可计算你在这个世界上已经存活多少天int ret4 = d3 - birth;cout << ret4 << endl;return 0;
}