Singleton pattern

单例模式，感觉看了还是不是很懂，尤其是什么多线程，什么锁。。

自己写了个单线程下的额单例模式，这个单例类是时间，用于程序的运行时告知系统当前时间。

至于头文件time.h看看能不能也研究研究。

参考：

http://blog.csdn.net/boyxiaolong/article/details/6645681

http://blog.yangyubo.com/2009/06/04/best-cpp-singleton-pattern/#id15

http://blog.csdn.net/lanxuezaipiao/article/details/16974151

main.cpp

#include <iostream>using namespace std;#include "Timer.h"int main() {    Timer& t = Timer::instance();    Timer& t_1 = Timer::instance();    //t = t_1;  // error: operator assignment is private, to ensure a singleton class    cout << endl;        string control;    while (1) {        cin >> control;        if (control == "end") {            break;        } else if (control == "show") {            t.show_time_here();        } else {            cout << "error order!" << endl;        }    }    cout << endl;        return 0;}

Timer.h

#ifndef __TIMER_H#define __TIMER_H#include <iostream>#include <time.h>  // to include this header file to get the system timeusing namespace std;class Timer {  public:    static Timer& instance() {        static Timer the_timer;  // with the static, the class the_timer will be alive in all the program since its birth, when the function instance is called, this can avoid making another timer        return the_timer;    }    void show_time_here() {        ti = time(NULL);        here_time = localtime(&ti);        gm_time = localtime(&ti);        cout << "The local time is: " << here_time->tm_year + 1900<< " " << here_time->tm_mon + 1<< " " << here_time->tm_mday << " " << here_time->tm_hour << " " << here_time->tm_min << " " << here_time->tm_sec << endl;  // remember to add 1900 to the year and 1 to the month(the starting points are 1900 and 0)        cout << "The local time is: " << gm_time->tm_year + 1900 << " " << gm_time->tm_mon + 1 << " " << gm_time->tm_mday << " " << gm_time->tm_hour << " " << gm_time->tm_min << " " << gm_time->tm_sec << endl;    }  private:    Timer() {        cout << "the timer is born." << endl;            }    Timer(Timer const&);  // to avoid this    Timer& operator=(Timer const&);  // to avoid this    ~Timer() {  // notice that the destructor is called after return 0 in main, cause static class the_timer is alive since its birth until the program is over        cout << "the timer died." << endl;    }    struct tm *here_time;  // tm is struct that contains time    struct tm *gm_time;    clock_t ti;    };#endif