C++ 事�g机制实现

zhuweisky — Sun, 11 Sep 2005 12:15:00 GMT

事�g是面向组件开发的必要�Ҏ��之一�Q�但C++不直接支持事�Ӟ��没关�p�，我自己实��C��一个，感觉很好用，分��n�l�大�Ӟ��
最开始打��用函数指针模拟事�g�Q�但�׃��C++中成员函数指针不能和void*�怺��{�Q�而且 typedef中不能含有模板，所以才不得已以接口�l�承实现。这��h��果也不错 �Q�）

一. 先看看事件接口定义和实现

#ifndef IEVENT_H
#define IEVENT_H

/*
以下各基��设施是在C++中事件机制的完整实现�Q�事件是面向�l��g开发的必要�Ҏ��之一�?BR>
�?nbsp;�?nbsp;者：sky
�?nbsp;   ��_��2005.06.22
修订旉��Q?005.06.22
*/

#include "../Collection/SafeArrayList.h"
template<class SenderType ,class ParaType> class EventPublisher ;

class NullType
{
};

// IEventHandler  是事件处理句柄，预定事�g的类从此接口�l�承以实��C��件处理函�?/SPAN>
template<class SenderType ,class ParaType>
interface IEventHandler
{

public:
virtual ~IEventHandler(){}
private:
virtual void HandleEvent(SenderType sender ,ParaType para)  = 0 ;
friend class EventPublisher<SenderType ,ParaType> ;
};

// IEvent 事�g预定斚w��过此接口预定事�?/SPAN>
template<class SenderType ,class ParaType>
interface IEvent
{
public:

virtual ~IEvent(){}
virtual void Register  (IEventHandler<SenderType ,ParaType>* handler) = 0 ;
virtual void UnRegister(IEventHandler<SenderType ,ParaType>* handler) = 0 ;
};

// IEventActivator 事�g发布斚w��过此接口触发事�?/SPAN>
template<class SenderType ,class ParaType>
interface IEventActivator
{
public:

virtual ~IEventActivator(){}
virtual void Invoke(SenderType sender ,ParaType para) = 0;
virtual int  HandlerCount() = 0;
virtual IEventHandler<SenderType ,ParaType>* GetHandler(int index) = 0;
};

// IEventPublisher 事�g发布方发布事件相当于��是发布一个IEventPublisher�z��cȝ��对象
// 不过仅仅��该对象的IEvent接口发布卛_��?/SPAN>
template<class SenderType ,class ParaType>
interface IEventPublisher : public IEvent<SenderType ,ParaType> ,public IEventActivator<SenderType ,ParaType>
{
};

// EventPublisher是IEventPublisher的默认实�?/SPAN>
template<class SenderType ,class ParaType>
class EventPublisher :public IEventPublisher<SenderType ,ParaType>
{
private:
SafeArrayList< IEventHandler<SenderType ,ParaType> > handerList ;
IEventHandler<SenderType ,ParaType>* innerHandler ;

public:
void Register(IEventHandler<SenderType ,ParaType>* handler)
{
  this->handerList.Add(handler) ;
}

void UnRegister(IEventHandler<SenderType ,ParaType>* handler)
{
  this->handerList.Remove(handler) ;
}

void Invoke(SenderType sender ,ParaType para)
{
  int count = this->handerList.Count() ;
  for(int i=0 ;i<count ;i++)
  {
   IEventHandler<SenderType ,ParaType>* handler = this->handerList.GetElement(i) ;
   handler->HandleEvent(sender ,para) ;
  }
}

int  HandlerCount()
{
  return this->handerList.Count() ;
}

IEventHandler<SenderType ,ParaType>* GetHandler(int index)
{
  return this->handerList.GetElement(index) ;
}
};

#endif

上面的实现是��显易懂的，关键是要注意IEventPublisher的双重��n份－�Q?事�g发布�Ҏ��好发布IEvent指针�l�外部，而该指针实际指向的是一个EventPublisher对象�Q�这是�ؓ了避免外部直接调用IEventActivator接口的方法�?BR>
�? 一个定时器�c�Timer�Q�演�C�如何发布事件。想必大安��知道定时器的用途了哦，�q�个Timer��像C#中的Timer�c�M��栗��?BR>

#ifndef TIMER_H
#define TIMER_H
/*
Timer 定时�?每经�q�一�D�|��定时间就触发事�g

�?nbsp;�?nbsp;者：sky
�?nbsp;   ��_��2005.06.22
修订旉��Q?005.06.22
*/
#include "IEvent.h"
#include "Thread.h"

void TimerThreadStart(void* para) ;

class Timer
{
private:
int spanInMillSecs ;
volatile bool isStop ;
volatile bool timerThreadDone ;

public:
friend void TimerThreadStart(void* para) ;
IEvent<Timer* ,NullType>* TimerTicked ;

Timer(int span_InMillSecs)
{
  this->isStop = true ;
  this->timerThreadDone = true ;
  this->spanInMillSecs = span_InMillSecs ;
  this->TimerTicked = new EventPublisher<Timer* ,NullType> ;
}

~Timer()
{
  this->Stop() ;
  delete this->TimerTicked ;
}

void Start()
{
  if(! this->isStop)
  {
   return ;
  }

  this->isStop = false ;
  Thread thread ;
  thread.Start(TimerThreadStart ,this) ;
  //unsigned int  dwThreadId ;
  //HANDLE hThread = (HANDLE)_beginthreadex(NULL, 0 , (unsigned int (_stdcall*)(void*))&TimerThreadStart , this, 0, &dwThreadId);

}

void Stop()
{
  if( this->isStop)
  {
   return ;
  }

  this->isStop = true ;

  //�{�待工作�U�程退�?/SPAN>
  while(! this->timerThreadDone)
  {
   Sleep(200) ;
  }
}

private:
void WorkerThread()
{
  this->timerThreadDone = false ;

  while(! this->isStop)
  {
   Sleep(this->spanInMillSecs) ;

   if(this->isStop)
   {
    break ;
   }

   NullType nullObj ;
   ((EventPublisher<Timer* ,NullType>*)this->TimerTicked)->Invoke(this ,nullObj) ;
  }

  this->timerThreadDone = true ;
}
};

void TimerThreadStart(void* para)
{
    Timer* timer = (Timer*)para ;
    timer->WorkerThread() ;
}
#endif

上面的示例清晰地说明了如何发布一个事�Ӟ��如何在适当的时候触发事�Ӟ��接下来看看如何预定事件�?BR>
�? 预定事�g例子

class TimerEventExample  :public IEventHandler<Timer* ,NullType> ,CriticalSection
{
private:
Timer* timer ;

public:
TimerEventExample(int checkSpan)
{
  this->timer = new Timer(checkSpan) ;
  this->timer->TimerTicked->Register(this) ;
}

~TimerEventExample()
{
  delete this->timer ;
}

private:
//处理定时事�g
void HandleEvent(Timer* sender ,NullType para)
{
  cout<<"Time ticked !"<<endl ;
}
};

到这里，已经��C++中的事�g机制的实现及使用讲清楚了。C#提供了很多便利的基础设施来支持组件开发，而在C++中，�q�些基础设施需要自己动手来构徏�Q�在拥有了这些设施之后，�怿�使用C++�q�行�l��g开发会��L��一炏V�?BR>

zhuweisky 2005-09-11 20:15 发表评论

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C++ 事�g机制实现