source: src/CodePatterns/Observer/Notification.hpp@ 7d0820

/*
 * Notification.hpp
 *
 *  Created on: Dec 1, 2011
 *      Author: heber
 */

#ifndef NOTIFICATION_HPP_
#define NOTIFICATION_HPP_

// include config.h
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <set>

class Channels;
class Observable;
class Observer;
class Relay;

/** Notifications are sort of news channels of an Observable.
 * Via the NOTIFY() macro updates can be transmitted in a specific channel.
 * Observers can subscribe to Notification in much the same way as they can to
 * the Observable itself. Usually, Notifications are used along
 * with the usual OBSERVE() macro to generate both the specific and
 * the global message of change.
 *
 * \note Notification::subjectKilled() needs to be called by owning Channels.
 * We use the passed on Observable instance to let Observers that have only 
 * signed on to single channel know when their observable has died.
 */
class Notification {
public:
  Notification(size_t _channelno);
  virtual ~Notification();

  size_t getChannelNo() const { return channelno; }

protected:

  void addObserver(Observer *target);
  void removeObserver(Observer *target);

private:
  //!> grant Observable access to notifyAll() and subjectKilled()
  friend class Observable;
  //!> grant Channels access to notifyAll() and subjectKilled()
  friend class Channels;
  //!> grant Relay access to notifyAll()
  friend class Relay;

  void notifyAll(Observable * const publisher);

  /** Informs channel subscribers about dstor call.
   *
   * This is meant to be called from Observable only.
   * Channels and Notifications are strictly attached to an Observable. Hence,
   * it makes no sense to inform them on their own. Especially, neither has
   * any knowledge on the publisher.
   *
   * \param *publisher Observable about to be destroyed
   */
  void subjectKilled(Observable * const publisher);

  /** Getter for the number of Observer for this notification (channel).
   *
   * \return number of added observers
   */
  size_t getNumberOfObservers() const
  { return targets.size(); }

private:
  typedef std::set<Observer*> targets_t;
  targets_t targets;
  const size_t channelno;
};



#endif /* NOTIFICATION_HPP_ */