Observer.h

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/***************************************************************************
 *   (c) Jürgen Riegel (juergen.riegel@web.de) 2002                        *   
 *                                                                         *
 *   This file is part of the FreeCAD CAx development system.              *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU Library General Public License (LGPL)   *
 *   as published by the Free Software Foundation; either version 2 of     *
 *   the License, or (at your option) any later version.                   *
 *   for detail see the LICENCE text file.                                 *
 *                                                                         *
 *   FreeCAD is distributed in the hope that it will be useful,            *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        * 
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU Library General Public License for more details.                  *
 *                                                                         *
 *   You should have received a copy of the GNU Library General Public     *
 *   License along with FreeCAD; if not, write to the Free Software        * 
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
 *   USA                                                                   *
 *                                                                         *
 *   Juergen Riegel 2002                                                   *
 ***************************************************************************/


#ifndef BASE_OBSERVER_H
#define BASE_OBSERVER_H

// Std. configurations

#include <assert.h>
#include <set>
#include <cstring>
#include <cstdio>


namespace Base
{

template <class MessageType> class Subject;


template <class _MessageType>
class Observer
{
public:

  Observer(){};

  virtual ~Observer(){};

  virtual void OnChange(Subject<_MessageType>& rCaller,_MessageType rcReason)=0;

  virtual void OnDestroy(Subject<_MessageType> & rCaller){}

  virtual const char *Name(void){return 0L;}
};

template <class _MessageType>
class Subject
{
public:

  typedef  Observer<_MessageType> ObserverType;
  typedef  _MessageType             MessageType;
  typedef  Subject<_MessageType>  SubjectType;   
     
  Subject(){};

  virtual ~Subject()
  {
    if (_ObserverSet.size() > 0)
    {
      printf("Not detached all observers yet\n");
      assert(0);
    }
  }

  void Attach(Observer<_MessageType> *ToObserv)
  {
#ifdef FC_DEBUG
    size_t count = _ObserverSet.size();
    printf("Attach observer %p\n", ToObserv);
    _ObserverSet.insert(ToObserv);
    if ( _ObserverSet.size() == count )
      printf("Observer %p already attached\n", ToObserv);
#else
    _ObserverSet.insert(ToObserv);
#endif
  }

  void Detach(Observer<_MessageType> *ToObserv)
  {
#ifdef FC_DEBUG
    size_t count = _ObserverSet.size();
    printf("Detach observer %p\n", ToObserv);
    _ObserverSet.erase(ToObserv);
    if ( _ObserverSet.size() == count )
      printf("Observer %p already detached\n", ToObserv);
#else
    _ObserverSet.erase(ToObserv);
#endif
  }

  void Notify(_MessageType rcReason)
  {
    for(typename std::set<Observer<_MessageType> * >::iterator Iter=_ObserverSet.begin();Iter!=_ObserverSet.end();Iter++)
      (*Iter)->OnChange(*this,rcReason);   // send OnChange-signal
  }

  Observer<_MessageType> * Get(const char *Name)
  {
    const char* OName;
    for(typename std::set<Observer<_MessageType> * >::iterator Iter=_ObserverSet.begin();Iter!=_ObserverSet.end();Iter++)
    {
      OName = (*Iter)->Name();   // get the name
      if(OName && strcmp(OName,Name) == 0)
        return *Iter;
    }

    return 0L;
  }

  void ClearObserver()
  {
    _ObserverSet.clear();
  }


protected:
  std::set<Observer <_MessageType> *> _ObserverSet;
};


} //namespace Base


#endif // BASE_OBSERVER_H