source: src/Patterns/Observer/Observable.hpp@ 40f2e6

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

#ifndef OBSERVABLE_HPP_
#define OBSERVABLE_HPP_

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

#include <map>
#include <set>
#include <string>

#include "Range.hpp"
#include "Observer/defs.hpp"
#include "Observer/Observer.hpp"

/**
 * An Observable implements all neccessary method for being observed.
 *
 * That is, it provides methods for signing on and of from an
 * Observable that can be used by any observer. The actual
 * observer-mechanism is handled at a central static place
 * to avoid memory issues when many observable are around but only few
 * are actually observed.
 */
class Observable : public Observer {
public:
  Observable(std::string _name);
  virtual ~Observable();

  /** This class is only used to distinguish from size_t in the overload.
   *
   * It encapsulates a const int (the priority level) and checks valid bounds
   * in constructor.
   *
   */
  class PriorityLevel {
  public:
    explicit PriorityLevel(const int i);
    ~PriorityLevel();

    const int level;
  private:
    static range<int> ValidRange;
  };

  /**
   * Sign an Observer on to this Observable. The Observer will be notified
   * whenever something inside the Observable changes. The Observer can
   * assign itself a priority for the changes in the range of -20:+20.
   * The Observer with lower priority will be called before the others,
   * same as with Unix nice-levels. This can be used when an Object
   * contains other objects that observe it (derived values), and these objects have
   * to recalculate their states before the changes should be propageted to the
   * UI. A default priority of 0 should be fine in most cases, since there is
   * ussually no need to order the update sequence.
   */
  virtual void signOn(Observer *target, PriorityLevel priority = PriorityDefault) const;

  /**
   * Sign of a previously signed on Observer. After this no more
   * updates will be recieved from that observer.
   */
  virtual void signOff(Observer *target) const;

  /**
   * Sign on for specialized notifications
   */
  virtual void signOn(Observer *target, size_t channelno) const;

  /**
   * Stop receiving a specialized notification
   */
  virtual void signOff(Observer *target, size_t channelno) const;

  /**
   * Ask an Observer if it is currently in a blocked state, i.e. if
   * Changes are in Progress, that are not yet published.
   */
  virtual bool isBlocked() const;

  Notification_ptr getChannel(size_t no) const;

protected:
  virtual void update(Observable *publisher);
  virtual void subjectKilled(Observable *publisher);

  virtual void notifyAll();
protected:
// Observer mechanism is done from a static central place
  /**
   * Internal method.
   * Do not call directly. Use OBSERVE macro instead
   */
  static void start_observer_internal(Observable *publisher);
  /**
   * Internal method.
   * Do not call directly. Use OBSERVE macro instead
   */
  static void finish_observer_internal(Observable *publisher);

  static void enque_notification_internal(Observable *publisher, Notification_ptr notification);

  typedef std::map<Observable*, Channels *> ChannelMap;
  static ChannelMap NotificationChannels;

  static PriorityLevel PriorityDefault;

private:
  typedef std::multimap<int,Observer*> callees_t;
  typedef std::set<Notification*> notificationSet;
  static std::map<Observable*, int> depth;
  static std::map<Observable*,callees_t> callTable;
  static std::map<Observable*,notificationSet> notifications;
  static std::set<Observable*> busyObservables;

  //! @cond
  // Structure for RAII-Style notification
public:
  /**
   * This structure implements the Observer-mechanism RAII-Idiom.
   * It triggers certain functions on creation and destruction so that
   * Observer mechanisms can be linked to scope block.
   */
  class _Observable_protector {
  public:
    _Observable_protector(Observable *);
    _Observable_protector(const _Observable_protector&);
    ~_Observable_protector();
  private:
    Observable *protege;
  };
  //! @endcond
};


// extra macro is necessary to work with __LINE__
#define PASTE(a,b) PASTE_HELPER(a,b)
#define PASTE_HELPER(a,b) a ## b
#define OBSERVE Observable::_Observable_protector PASTE(_scope_obs_protector_,__LINE__)(this)
#define NOTIFY(channelno) do{Observable::enque_notification_internal(this,NotificationChannels[this]->getChannel(channelno));}while(0)
#define LOCK_OBSERVABLE(observable) Observable::_Observable_protector PASTE(_scope_obs_protector_,__LINE__)(&(observable))

#endif /* OBSERVABLE_HPP_ */