notificationcenter.h

This software aims to create an applet and panel tools to manage a wireless interface card, such as

//
// NotificationCenter.h
//
// $Id: //poco/Main/Foundation/include/Foundation/NotificationCenter.h#5 $
//
// Definition of the NotificationCenter class.
//
// Copyright (c) 2004, Guenter Obiltschnig/Applied Informatics.
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 
// 3. Redistributions in any form must be accompanied by information on
//    how to obtain complete source code for this software and any
//    accompanying software that uses this software.  The source code
//    must either be included in the distribution or be available for no
//    more than the cost of distribution plus a nominal fee, and must be
//    freely redistributable under reasonable conditions.  For an
//    executable file, complete source code means the source code for all
//    modules it contains.  It does not include source code for modules or
//    files that typically accompany the major components of the operating
//    system on which the executable file runs.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//


#ifndef Foundation_NotificationCenter_INCLUDED
#define Foundation_NotificationCenter_INCLUDED


#ifndef Foundation_Foundation_INCLUDED
#include "Foundation/Foundation.h"
#endif
#ifndef Foundation_Mutex_INCLUDED
#include "Foundation/Mutex.h"
#endif
#ifndef STD_LIST_INCLUDED
#include <list>
#define STD_LIST_INCLUDED
#endif


Foundation_BEGIN


class Notification;
class AbstractObserver;


class Foundation_API NotificationCenter
	/// A NotificationCenter is essentially a notification dispatcher. 
	/// It notifies all observers of notifications meeting specific criteria.
	/// This information is encapsulated in Notification objects.
	/// Client objects register themselves with the notification center as observers of 
	/// specific notifications posted by other objects. When an event occurs, an object 
	/// posts an appropriate notification to the notification center. The notification  
	/// center invokes the registered method on each matching observer, passing the notification 
	/// as argument.
	///
	/// The order in which observers receive notifications is undefined. 
	/// It is possible for the posting object and the observing object to be the same.
	/// The NotificationCenter delivers notifications to observers synchronously. 
	/// In other words the postNotification() method does not return until all observers have 
	/// received and processed the notification. 
	/// If an observer throws an exception while handling a notification, the NotificationCenter
	/// stops dispatching the notification and postNotification() rethrows the exception.
	///
	/// In a multithreaded scenario, notifications are always delivered in the thread in which the 
	/// notification was posted, which may not be the same thread in which an observer registered itself.
	///
	/// The NotificationCenter class is basically a C++ implementation of the NSNotificationCenter class
	/// found in Apple's Cocoa (or OpenStep).
	///
	/// While handling a notification, an observer can unregister itself from the notification center,
	/// or it can register or unregister other observers. Observers added during a dispatch cycle
	/// will not receive the current notification.
	///
	/// The method receiving the notification must be implemented as
	///     void handleNotification(MyNotification* pNf);
	/// The handler method gets co-ownership of the Notification object
	/// and must release it when done. This is best done with an AutoPtr:
	///     void MyClass::handleNotification(MyNotification* pNf)
	///     {
	///         AutoPtr<MyNotification> nf(pNf);
	///         ...
	///     }
{
public:
	NotificationCenter();
		/// Creates the NotificationCenter.

	~NotificationCenter();
		/// Destroys the NotificationCenter.

	void addObserver(const AbstractObserver& observer);
		/// Registers an observer with the NotificationCenter.
		/// Usage:
		///     Observer<MyClass, MyNotification> obs(*this, &MyClass::handleNotification);
		///     notificationCenter.addObserver(obs);

	void removeObserver(const AbstractObserver& observer);
		/// Unregisters an observer with the NotificationCenter.

	void postNotification(Notification* pNotification);
		/// Posts a notification to the NotificationCenter.
		/// The NotificationCenter then delivers the notification
		/// to all interested observers.
		/// If an observer throws an exception, dispatching terminates
		/// and the exception is rethrown to the caller.
		/// Ownership of the notification object is claimed and the
		/// notification is released before returning. Therefore,
		/// a call like
		///    notificationCenter.postNotification(new MyNotification);
		/// does not result in a memory leak.

	static NotificationCenter& defaultCenter();
		/// Returns a reference to the default
		/// NotificationCenter.

private:
	typedef std::list<AbstractObserver*> ObserverList;

	ObserverList _observers;
	Mutex        _mutex;
};


Foundation_END


#endif // Foundation_NotificationCenter_INCLUDED