dispatcher.php

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<?php
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// | Copyright (c) 2005, Bertrand Mansion                                  |
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// +-----------------------------------------------------------------------+
// | Author: Bertrand Mansion <[e-mail]>                       |
// |         Stephan Schmidt <[e-mail]>                               |
// +-----------------------------------------------------------------------+
//
// $Id: Dispatcher.php 163 2008-01-14 04:40:16Z matt $

require_once 'Event/Notification.php';

/**
 * Pseudo 'static property' for Notification object
 * @global array $GLOBALS["_Event_Dispatcher"]
 */
$GLOBALS['_Event_Dispatcher'] = array(
                                  'NotificationClass' => 'Event_Notification'
                                     );

/**
 * Registers a global observer
 */
define('EVENT_DISPATCHER_GLOBAL', '');

/**
 * Dispatch notifications using PHP callbacks
 *
 * The Event_Dispatcher acts acts as a notification dispatch table.
 * It is used to notify other objects of interesting things, if
 * they meet certain criteria. This information is encapsulated 
 * in {@link Event_Notification} objects. Client objects register 
 * themselves with the Event_Dispatcher as observers of specific
 * notifications posted by other objects. When an event occurs,
 * an object posts an appropriate notification to the Event_Dispatcher.
 * The Event_Dispatcher dispatches a message to each
 * registered observer, passing the notification as the sole argument.
 *
 * The Event_Dispatcher is actually a combination of three design
 * patterns: the Singleton, {@link http://c2.com/cgi/wiki?MediatorPattern Mediator},
 * and Observer patterns. The idea behind Event_Dispatcher is borrowed from 
 * {@link http://developer.apple.com/documentation/Cocoa/Conceptual/Notifications/index.html Apple's Cocoa framework}.
 *
 * @category   Event
 * @package    Event_Dispatcher
 * @author     Bertrand Mansion <[e-mail]>
 * @author     Stephan Schmidt <[e-mail]>
 * @copyright  1997-2005 The PHP Group
 * @license    http://www.opensource.org/licenses/bsd-license.php BSD License
 * @version    Release: @package_version@
 * @link       http://pear.php.net/package/Event_Dispatcher
 */
class Event_Dispatcher
{
    /**
     * Registered observer callbacks
     * @var array
     * @access private
     */
    var $_ro = array();
    
    /**
     * Pending notifications
     * @var array
     * @access private
     */
    var $_pending = array();

    /**
     * Nested observers
     * @var array
     * @access private
     */
    var $_nestedDispatchers = array();

    /**
     * Name of the dispatcher
     * @var string
     * @access private
     */
    var $_name = null;

    /**
     * Class used for notifications
     * @var string
     * @access private
     */
    var $_notificationClass = null;

    /**
     * PHP4 constructor
     *
     * Please use {@link getInstance()} instead.
     *
     * @access  private
     * @param   string      Name of the notification dispatcher.
     */
//    function Event_Dispatcher($name)
//    {
//        Event_Dispatcher::__construct($name);
//    }

    /**
     * PHP5 constructor
     *
     * Please use {@link getInstance()} instead.
     *
     * @access  private
     * @param   string      Name of the notification dispatcher.
     */
    function __construct($name)
    {
        $this->_name = $name;
        $this->_notificationClass = $GLOBALS['_Event_Dispatcher']['NotificationClass'];
    }

    /**
     * Returns a notification dispatcher singleton
     *
     * There is usually no need to have more than one notification
     * center for an application so this is the recommended way
     * to get a Event_Dispatcher object.
     *
     * @param string    Name of the notification dispatcher.
     *                  The default notification dispatcher is named __default.
     * 
     * @return object Event_Dispatcher
     */
    static function getInstance($name = '__default')
    {
        static $dispatchers = array();

        if (!isset($dispatchers[$name])) {
            $dispatchers[$name] = new Event_Dispatcher($name);
        }

        return $dispatchers[$name];
    }

    /**
     * Registers an observer callback
     *
     * This method registers a {@link http://www.php.net/manual/en/language.pseudo-types.php#language.types.callback callback}
     * which is called when the notification corresponding to the
     * criteria given at registration time is posted.
     * The criteria are the notification name and eventually the 
     * class of the object posted with the notification.
     *
     * If there are any pending notifications corresponding to the criteria
     * given here, the callback will be called straight away.
     *
     * If the notification name is empty, the observer will receive all the
     * posted notifications. Same goes for the class name.
     *
     * @access  public
     * @param   mixed       A PHP callback
     * @param   string      Expected notification name, serves as a filter
     * @param   string      Expected contained object class, serves as a filter
     * @return void
     */
    function addObserver($callback, $nName = EVENT_DISPATCHER_GLOBAL, $class = null)
    {
        if (is_array($callback)) {
            if (is_object($callback[0])) {
                // Note : PHP4 does not allow correct object comparison so
                // only the class name is used for registration checks.
                $reg = get_class($callback[0]).'::'.$callback[1];
            } else {
                $reg = $callback[0].'::'.$callback[1];
            }
        } else {
            $reg = $callback;
        }

        $this->_ro[$nName][$reg] = array(
                                    'callback' => $callback,
                                    'class'    => $class
                                    );

        // Post eventual pending notifications for this observer
        if (isset($this->_pending[$nName])) {
            foreach (array_keys($this->_pending[$nName]) as $k) {
                $notification =& $this->_pending[$nName][$k];
                if (!$notification->isNotificationCancelled()) {
                    $objClass = get_class($notification->getNotificationObject());
                    if (empty($class) || strcasecmp($class, $objClass) == 0) {
                        call_user_func_array($callback, array(&$notification));
                        $notification->increaseNotificationCount();
                    }
                }
            }
        }
    }

    /**
     * Creates and posts a notification object
     *
     * The purpose of the optional associated object is generally to pass
     * the object posting the notification to the observers, so that the 
     * observers can query the posting object for more information about
     * the event.
     *
     * Notifications are by default added to a pending notification list.
     * This way, if an observer is not registered by the time they are 
     * posted, it will still be notified when it is added as an observer.
     * This behaviour can be turned off in order to make sure that only
     * the registered observers will be notified.
     *
     * The info array serves as a container for any kind of useful 
     * information. It is added to the notification object and posted along.
     *
     * @access  public