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misc/observer.h

Go to the documentation of this file.

#ifndef MISC_OBSERVER_H
#define MISC_OBSERVER_H

/*

  GLT OpenGL C++ Toolkit (LGPL)
  Copyright (C) 2000-2002 Nigel Stewart  

  Email: nigels.com@gmail.com   
  WWW:   http://www.nigels.com/glt/

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

*/

#include <glt/config.h>

#include <cassert>
#include <list>

class GltSubject;

class GltObserverAbstract 
{
    friend class GltSubject;

protected:

    GltObserverAbstract();
    GltObserverAbstract(const GltObserverAbstract &);
    virtual ~GltObserverAbstract();

    GltObserverAbstract &operator=(const GltObserverAbstract &);

    void observe(GltSubject &subject);
    void forget (GltSubject &subject);

    virtual void OnNotify(const void *subject) = 0;

    std::list<GltSubject *> _subjects;
};

template<class T>
class GltObserver : public GltObserverAbstract
{
public:

    GltObserver() {}
    ~GltObserver() {}

    void observe(T &subject) { GltObserverAbstract::observe(subject); }
    void forget (T &subject) { GltObserverAbstract::forget (subject); }
    
    virtual void OnNotify(const T *subject) = 0;

protected:

    void OnNotify(const void *subject)
    {
        OnNotify((const T *) subject);
    }
};

class GltSubject
{
    friend class GltObserverAbstract;

public:
    GltSubject();
    GltSubject(const GltSubject &);
    ~GltSubject();

    GltSubject &operator=(const GltSubject &);

    void notify(const void *object);

private:

    std::list<GltObserverAbstract *> _observers;
};

#define NOTIFY notify(this)

#endif

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