After learning classes and objects, I wrote a date class

●🧑 Personal home page : You're handsome. You say it first .
● Welcome to like, pay attention to collection
● Both chose the distance , We will only struggle ahead .
●🤟 You are welcome to write to me if you have any questions ！
●🧐 Copyright ： This paper is written by [ You're handsome. You say it first .] original ,CSDN First episode , Infringement must be investigated .

🧨1. Design thinking

The date class we designed this time is about to realize Judging the size of the date 、 Addition and subtraction of date 、 Input and output of date 、 The date corresponds to the day of the week . This will put us in front Classes and objects Apply the knowledge points learned in , Let's have a deeper understanding of classes and objects .

2.Date Class framework

Date.h

#pragma once
#include<iostream>
using namespace std;
class Date
{
    
	//  Friend function 
	friend ostream& operator<<(ostream& out, const Date& d);
	friend istream& operator>>(istream& in, Date& d);
public:
	Date(int year = 1, int month = 1, int day = 1);
	void Print() const;
	int GetMonthDay(int year, int month) 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;
	bool operator!=(const Date& d)const;
	Date& operator+=(int day);
	Date operator+(int day)const;
	Date& operator-=(int day);
	Date operator-(int day)const;
	Date& operator++();
	Date operator++(int);
	Date& operator--();
	Date operator--(int);
	int operator-(const Date& d) const;
	void PrintWeekDay() const;
private:
	int _year;
	int _month;
	int _day;
};

3. Class member function implementation

These implementations are placed in Date.cpp In the document
The first interface to be implemented is Constructors

void Date::Print() const
{
    
	cout << _year << "-" << _month << "-" << _day << endl;
}
Date::Date(int year, int month, int day)
{
    
	_year = year;
	_month = month;
	_day = day;

	if (!(_year >= 0
		&& (month > 0 && month < 13)
		&& (day > 0 && day <= GetMonthDay(year, month))))
	{
    
		cout << " Illegal date ->";
		Print();
	}
}

Next we're going to achieve Date The core interface in the class :GetMonthDay, This interface when you enter year and month when , It will return the corresponding number of days , Here is the problem of weekdays and leap years .C At the language stage, we learned to judge leap years , There is a pithy formula : A leap in four years , A hundred years without Leap , Four hundred years later , To implement it in code is
year % 4 == 0 && year % 100 != 0 || year % 400 == 0

int Date::GetMonthDay(int year, int month) const
{
    
	static int monthDayArray[13] = {
     0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
	int day = monthDayArray[month];
	if (month == 2 && ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)))
	{
    
		day += 1;
	}

	return day;
}

Complete the implementation of this interface , The next interface is easy .
heavy load > Operator

bool Date::operator>(const Date& d)const
{
    
	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;
	}
	else
	{
    
		return false;
	}
}

heavy load == Operator

bool Date::operator==(const Date& d)const
{
    
	return _year == d._year
		&& _month == d._month
		&& _day == d._day;
}

🥎 heavy load < Operator

bool Date::operator<(const Date& d)  const
{
    
	return !(*this >= d);
}

heavy load >= Operator

bool Date::operator>=(const Date& d)  const
{
    
	return *this > d || *this == d;
}

heavy load <= Operator

bool Date::operator<=(const Date& d)  const
{
    
	return  !(*this > d);
}

heavy load != Operator

bool Date::operator!=(const Date& d)  const
{
    
	return  !(*this == d);
}

🤿 heavy load += Operator

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

	return *this;
}

heavy load + Operator

Date Date::operator+(int day)  const
{
    
	Date ret(*this);
	//ret.operator+=(day);
	ret += day;

	return ret;
}

🥌 heavy load -= Operator

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);
	}

	return *this;
}

heavy load - Operator

// Calculate the date after subtracting a few days 
Date Date::operator-(int day)  const
{
    
	Date ret(*this);
	ret -= day;

	return ret;
}
// Calculate the date difference 
int Date::operator-(const Date& d)  const
{
    
	Date max = *this;
	Date min = d;
	int flag = 1;

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

	int count = 0;
	while (min != max)
	{
    
		++min;
		++count;
	}

	return count * flag;
}

heavy load In front of ++ Operator

Date& Date::operator++()
{
    
	*this += 1;

	return *this;
}

heavy load After ++ Operator

Date Date::operator++(int)
{
    
	Date ret(*this);
	*this += 1;

	return ret;
}

heavy load In front of -- Operator

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

🪀 heavy load After -- Operator

Date Date::operator--(int)
{
    
	Date ret(*this);
	*this -= 1;
	return ret;
}

Output day of the week

void Date::PrintWeekDay() const
{
    
	const char* arr[] = {
     " Monday ", " Tuesday ", " Wednesday ", " Thursday ", " Friday ", " Saturday ", " Sunday " };
	//Date start(1900, 1, 1);
	//int count = *this - start;
	int count = *this - Date(1900, 1, 1);

	cout << arr[count % 7] << endl;
}

🪅 heavy load << Operator

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

heavy load >> Operator

istream& operator>>(istream& in,Date& d)
{
    
	in >> d._year >> d._month >> d._day;
	return in;
}

Date.h and Date.cpp After the content in the document is realized , The whole date class is finished . Then we can Test.cpp The file calls and runs . I think it's too simple , It can also be in Test.cpp Write a menu in .

Those who like this article can give One key, three links Like, focus on collection