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Observer.h

//
// Observer.h
//
// $Id: //poco/1.2/Foundation/include/Poco/Observer.h#2 $
//
// Library: Foundation
// Package: Notifications
// Module:  NotificationCenter
//
// Definition of the Observer class template.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_Observer_INCLUDED
#define Foundation_Observer_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/AbstractObserver.h"


namespace Poco {


template <class C, class N>
00051 class Observer: public AbstractObserver
      /// This template class implements an adapter that sits between
      /// a NotificationCenter and an object receiving notifications
      /// from it. It is quite similar in concept to the 
      /// RunnableAdapter, but provides some NotificationCenter
      /// specific additional methods.
      /// See the NotificationCenter class for information on how
      /// to use this template class.
      ///
      /// Instead of the Observer class template, you might want to
      /// use the NObserver class template, which uses an AutoPtr to
      /// pass the Notification to the callback function, thus freeing
      /// you from memory management issues.
{
public:
      typedef void (C::*Callback)(N*);

      Observer(C& object, Callback method): 
            _pObject(&object), 
            _method(method)
      {
      }
      
      Observer(const Observer& observer):
            AbstractObserver(observer),
            _pObject(observer._pObject), 
            _method(observer._method)
      {
      }
      
      ~Observer()
      {
      }
      
      Observer& operator = (const Observer& observer)
      {
            if (&observer != this)
            {
                  _pObject = observer._pObject;
                  _method  = observer._method;
            }
            return *this;
      }
      
      void notify(Notification* pNf) const
      {
            N* pCastNf = dynamic_cast<N*>(pNf);
            if (pCastNf)
            {
                  pCastNf->duplicate();
                  (_pObject->*_method)(pCastNf);
            }
      }
      
      bool equals(const AbstractObserver& abstractObserver) const
      {
            const Observer* pObs = dynamic_cast<const Observer*>(&abstractObserver);
            return pObs && pObs->_pObject == _pObject && pObs->_method == _method;
      }

      bool accepts(Notification* pNf) const
      {
            return dynamic_cast<N*>(pNf) != 0;
      }
      
      AbstractObserver* clone() const
      {
            return new Observer(*this);
      }
      
private:
      Observer();

      C*       _pObject;
      Callback _method;
};


} // namespace Poco


#endif // Foundation_Observer_INCLUDED

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