C++编程之约定俗成的习惯（1）

说明：C++的类定义中，可以任意安排成员函数和成员变量的位置，一般我们将成员变量都设置成私有的，而将大多成员函数都设置为公有的。其中，公有成员和私有成员顺序的安排没有统一的标准，但是我们倾向于将成员函数放在成员变量之前。

代码示例：

//包含一个非常简单的类的演示程序
//类DayOfYear
#include<iostream>
#include<cstdlib>
using namespace std;
class DayOfYear
{
public:
    void input();
    void output();
    void set(int newMonth,int newDay);
    //前提条件:newMonth和newDay可以构成一个合法的日期
    void set(int newMonth);
    //前提条件:1<=newMonth<=12
    //运行结果: 日期被设定为参数给定月份的第一天

    int geyMonthNumber();
    int getDay();

private:
    int month;
    int day;
};

int main()
{
    DayOfYear today,bachBirthday;
    cout<<"Enter today's date:
";
    today.input();
    cout<<"Today's date is ";
    today.output();
    cout<<endl;
    bachBirthday.set(3,21);
    cout<<"J.S Bach's birthday is ";
    bachBirthday.output();
    cout<<endl;

    if(today.geyMonthNumber()==bachBirthday.geyMonthNumber()&&today.getDay()==bachBirthday.getDay())
    {
        cout<<"Happy Birthday Johann Sebastian!
";
    }
    else
    {
        cout<<"Happy Unbirthday Johann Sebastian!
";
    }

    return 0;
}

//使用iostream和cstdlib
void DayOfYear::set(int newMonth,int newDay)
{
    if((newMonth>=1)&&(newMonth<=12))
    {
        month=newMonth;
    }
    else
    {
        cout<<"Illegal month value!Program aborted.
";
        exit(1);
    }
    if((newDay>=1)&&(newDay<=31))
    {
        day=newDay;
    }
    else
    {
        cout<<"Illegal day value!Program aborted.
";
        exit(1);
    }
}

void DayOfYear::set(int newMonth)
{
    if((newMonth>=1)&&(newMonth<=12))
    {
        month=newMonth;
    }
    else
    {
        cout<<"Illegal month value!Program aborted.
";
        exit(1);
    }
    day=1;
}
int DayOfYear::geyMonthNumber()
{
    return month;
}
int DayOfYear::getDay()
{
    return day;
}
void DayOfYear::input()
{
    cout<<"Enter the month as a number:";
    cin>>month;
    cout<<"Enter the day of the month:";
    cin>>day;
    if((month<1)||(month>12)||(day<1)||(day>31))
    {
        cout<<"Illegal date!Program aborted.
";
        exit(1);
    }
}
void DayOfYear::output()
{
    switch(month)
    {
    case 1:
        cout<<"January ";
        break;
    case 2:
        cout<<"February ";
        break;
    case 3:
        cout<<"March ";
        break;
    case 4:
        cout<<"April ";
        break;
    case 5:
        cout<<"May ";
        break;
    case 6:
        cout<<"June ";
        break;
    case 7:
        cout<<"July ";
        break;
    case 8:
        cout<<"August ";
        break;
    case 9:
        cout<<"September ";
        break;
    case 10:
        cout<<"October ";
        break;
    case 11:
        cout<<"November ";
        break;
    case 12:
        cout<<"Decemebr ";
        break;
    default:
        cout<<"Error in DayOfYear::output.";
    }

    cout<<day;
}