source: XMLIO_V2/external/src/POCO/Foundation.save/Poco/NotificationCenter.h @ 80

//
// NotificationCenter.h
//
// $Id: //poco/1.3/Foundation/include/Poco/NotificationCenter.h#3 $
//
// Library: Foundation
// Package: Notifications
// Module:  NotificationCenter
//
// Definition of the NotificationCenter class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_NotificationCenter_INCLUDED
#define Foundation_NotificationCenter_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Notification.h"
#include "Poco/Mutex.h"
#include "Poco/SharedPtr.h"
#include <vector>
#include <cstddef>


namespace Poco {


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);
        ///         ...
        ///     }
        ///
        /// Alternatively, the NObserver class template can be used to register a callback
        /// method. In this case, the callback method receives the Notification in an
        /// AutoPtr and thus does not have to deal with object ownership issues:
        ///     void MyClass::handleNotification(const AutoPtr<MyNotification>& 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);
                ///
                /// Alternatively, the NObserver template class can be used instead of Observer.

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

        void postNotification(Notification::Ptr 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.

        bool hasObservers() const;
                /// Returns true iff there is at least one registered observer.
                ///
                /// Can be used to improve performance if an expensive notification
                /// shall only be created and posted if there are any observers.
                
        std::size_t countObservers() const;
                /// Returns the number of registered observers.
                
        static NotificationCenter& defaultCenter();
                /// Returns a reference to the default
                /// NotificationCenter.

private:
        typedef Poco::SharedPtr<AbstractObserver> AbstractObserverPtr;
        typedef std::vector<AbstractObserverPtr> ObserverList;

        ObserverList  _observers;
        mutable Mutex _mutex;
};


} // namespace Poco


#endif // Foundation_NotificationCenter_INCLUDED