如何通过更新静态变量来更新实例？

Question

我的班级时间可以根据静态变量以一天中的小时数和一小时内的分钟数显示时间。我希望能够通过简单地更改我的静态变量来打印更新的时间。

在我的 main() 中，我想根据默认的静态变量（一天 24 小时，一小时 60 分钟）声明一些 Time 实例。

Time a;
Time b(5);
Time c(61);

cout << "a = " << a << "\t";
cout << "b = " << b << "\t";
cout << "c = " << c << "\n";

// output is a =  0:00  b =  0:05 c =  1:01

Time::set_hr_in_day(60);

Time::set_min_in_hr(24);
cout << "a = " << a << "\t";
cout << "b = " << b << "\t";
//output should be a =  0:00    b =  0:05   c =  2:13

但是，代码仍然会打印出默认静态变量的数字。

关于如何解决此问题的任何想法？顺便说一句，我正在尝试创建一个类来测试给定的驱动程序，因此不能更改我的主要功能。

这是我的其余代码：

头文件

#ifndef TIME_H
#define TIME_H

#include <iostream>

using namespace std;

class Time {
private:
    int hour;
    int minute;
    static int dayhrs;
    static int hrsmin;

public:

    Time();
    Time(int min);
    Time(int hr, int min);
    Time(double hrs);
    int minutes() { return minute; };
    int hours() { return hour; };

    static void set_hr_in_day(int hr);
    static void set_min_in_hr(int min);
    static int dailyhr() { return dayhrs; };
    static int hourlymin() { return hrsmin; };

friend ostream& operator<<(ostream& os, const Time& t);


};



#endif

实现

#include "time.h"
#include <iostream>

using namespace std;

int Time::dayhrs = 24;//default
int Time::hrsmin = 60;

void Time::set_hr_in_day(int hr) {
    dayhrs = hr;
}

void Time::set_min_in_hr(int min) {
    hrsmin = min;
}


Time::Time() {
    hour = 0;
    minute = 0;
}

Time::Time(int min) {
    if (min > (Time::hourlymin() - 1)) {
        hour = min / Time::hourlymin();
        minute = min % Time::hourlymin();
    }
    else {
        hour = 0;
        minute = min;
    }

}

Time::Time(int hr, int min) {
    if (min > (Time::hourlymin() - 1)) {
        hour = min / Time::hourlymin() + hr;
        minute = min % Time::hourlymin();
    }
    else {
        hour = hr;
        minute = min;
    }

    if (hour > (Time::dailyhr() - 1))
        hour = hour % (Time::dailyhr());
}

Time::Time(double hrs) {
    double fraction = 0;
    fraction = hrs - (int)hrs;
    minute = fraction * Time::hourlymin();
    if (fraction * Time::hourlymin() - (int)(fraction * Time::hourlymin()) >= 0.5)
        minute += 1;
    hour = hrs - fraction;
    if (hour > (Time::dailyhr() - 1))
        hour = hour % (Time::dailyhr());
}



ostream& operator<<(ostream& os, const Time& t)
{
    if (t.minute > 9)
        os << t.hour << ":" << t.minute;
    else
        os << t.hour << ":0" << t.minute;
    return os;
}

司机

#include <iostream>
#include "time.h"

using std::cout;

int main() {
    cout << "*****************************************\n";
    cout << "Welcome to 'San Angel'!\n";
    cout << "[ 1 day = 24 hours, 1 hour = 60 minutes ]\n\n";

    Time a;
    Time b(5);
    Time c(61);
    Time d(47, 59);
    Time X(5.0);
    Time Y(1.5);
    Time Z(25.1);

    cout << "a = " << a << "\t";
    cout << "b = " << b << "\t";
    cout << "c = " << c << "\n";
    cout << "d = " << d << "\t";
    cout << "X = " << X << "\t";
    cout << "Y = " << Y << "\n";
    cout << "\t\tZ = " << Z << "\n";


    Time::set_hr_in_day(60);
    Time::set_min_in_hr(24);
    cout << "*****************************************\n";
    cout << "Welcome to the land of the remembered!\n";
    cout << "[ 1 day = 60 hours, 1 hour = 24 minutes ]\n\n";

    cout << "a = " << a << "\t";
    cout << "b = " << b << "\t";
    cout << "c = " << c << "\n";
    cout << "d = " << d << "\t";
    cout << "X = " << X << "\t";
    cout << "Y = " << Y << "\n";
    cout << "\t\tZ = " << Z << "\n";

return 0;

}
/**

OUTPUT:

*****************************************
Welcome to 'San Angel'!
[ 1 day = 24 hours, 1 hour = 60 minutes ]

a =  0:00   b =  0:05   c =  1:01
d = 23:59   X =  5:00   Y =  1:30
Z =  1:06
*****************************************
Welcome to the land of the remembered!
[ 1 day = 60 hours, 1 hour = 24 minutes ]

a =  0:00   b =  0:05   c =  2:13
d = 59:23   X = 12:12   Y =  3:18
Z =  2:18 */

Answer 1

您只在构造函数中执行计算。当您稍后修改静态变量时，您不会自动重新计算结果。

一种可能的解决方案是将值存储在构造函数中，然后在写入流时进行实际计算。