怎么根据当前系统时间对数据成员如year进行初始化而不只是输出字符串？

怎么根据当前系统时间对数据成员如year进行初始化而不只是输出字符串？

思路：时区做了一个简单的转换，目前用系统当前时间（time系统调用获取的秒数）加上指定时区偏移，然后通过gmtime转换为UTC时间（即GMT+0时间）。前提条件是要求的时区数量有限，而且与GMT时间偏差已知。

如果要实现一个适用于各个时区的对象，会很麻烦，可能最少需要一天时间。不过有人已经写了现成的，如果需要可以参考一下github muduo项目。思路是读取/usr/share/zoneinfo/下面的时区文件，将其转换为local time。

以下代码适用于Unix/Linux系统，设计Time class，满足要求的6点。

#include <iostream>
#include <sys/time.h>

using namespace std;

enum class TimeZoneOffset : int
{
    Greenwich = 0,
    Beijing = 8,
    NewYork = -5,
    Tokyo = 9,
    Paris = 2,
};

class Time
{
public:
    explicit Time(TimeZoneOffset zone = TimeZoneOffset::Greenwich)
    {
        time_t now_time;
        tm* tmptr;

        time(&now_time); // 获取当前系统时间
        now_time += static_cast<int>(zone) * 3600;
        tmptr = gmtime(&now_time); // 转换为UTC时间
        if (!tmptr) {
            perror("gmtime error");
            exit(-1);
        }
        else {
            year = tmptr->tm_year + 1900;
            month = tmptr->tm_mon + 1;
            day = tmptr->tm_mday;
            hour = tmptr->tm_hour;
            minute = tmptr->tm_min;
            second = tmptr->tm_sec;
        }
    }

    int get_year() const {
        return year;
    }
    int get_month() const {
        return month;
    }
    int get_day() const {
        return day;
    }
    int get_hour() const {
        return hour;
    }
    int get_minute() const {
        return minute;
    }
    int get_second() const {
        return second;
    }

    void print() {
        printf("%4d-%02d-%02d %02d:%02d:%02d\n", 
            year, month, day,
            hour, minute, second);
    }

private:
    int hour;
    int minute;
    int second;
    int year;
    int month;
    int day;
};

int main()
{
    Time t0;
    t0.print();

    Time t1(TimeZoneOffset::Beijing);
    t1.print();

    Time t2(TimeZoneOffset::NewYork);
    t2.print();

    Time t3(TimeZoneOffset::Tokyo);
    t3.print();

    Time t4(TimeZoneOffset::Paris);
    t4.print();
    return 0;
}

测试结果：

2022-05-22 15:56:04
2022-05-22 23:56:04
2022-05-22 10:56:04
2022-05-23 00:56:04
2022-05-22 17:56:04

拿去

#include <iostream>
using namespace std;
class Time
{
public:
Time();
Time(int h, int m ,int s);
Time operator +(Time &t1);
Time operator >>(Time &t1);
Time operator <<(Time &t1);
void setHour(int h )
{
hour=h;
}
void setMinute(int m)
{
minute=m;
}
void setSecond(int s)
{
second=s;
}
int getHour()
{
return hour;
}
int getMinute()
{
return minute;
}
int getSecond()
{
return second;
}
private:
int hour;
int minute;
int second;
};
Time::Time()
{
hour=0;
minute=0;
second=0;
}
Time::Time(int h, int m ,int s)
{
hour=h;
minute=m;
second=s;
}
Time Time::operator +(Time &t1)
{
return Time(hour+t1.getHour(),minute+t1.getMinute(),second+t1.getSecond());
}
Time Time::operator >>(Time &t1)
{
int a,b,c;
cout<<"inputTime1:"<<endl;
cin>>a>>b>>c;
hour=a;
minute=b;
second=c;
cout<<"inputTime2:"<<endl;
cin>>a>>b>>c;
t1.setHour(a);
t1.setMinute(b);
t1.setSecond(c);
return Time(hour+t1.getHour(),minute+t1.getMinute(),second+t1.getSecond());
}
Time Time::operator <<(Time &t1)
{
cout<<t1.getHour()<<':'<<t1.getMinute()<<':'<<t1.getSecond()<<endl;
return Time(hour+t1.getHour(),minute+t1.getMinute(),second+t1.getSecond());
}
int main()
{
Time time1(1,2,3);
Time time2(2,3,4);
Time time3;
time3 = time1+time2;
time3 = time1>>time2;
time3<<(time1+time2);
}