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   1  <?php
   2  /**
   3  * @version        $Id:observer.php 6961 2007-03-15 16:06:53Z tcp $
   4  * @package        Joomla.Framework
   5  * @subpackage    Base
   6  * @copyright    Copyright (C) 2005 - 2010 Open Source Matters. All rights reserved.
   7  * @license        GNU/GPL, see LICENSE.php
   8  * Joomla! is free software. This version may have been modified pursuant
   9  * to the GNU General Public License, and as distributed it includes or
  10  * is derivative of works licensed under the GNU General Public License or
  11  * other free or open source software licenses.
  12  * See COPYRIGHT.php for copyright notices and details.
  13  */
  14  
  15  // Check to ensure this file is within the rest of the framework
  16  defined('JPATH_BASE') or die();
  17  
  18  /**
  19   * Abstract observer class to implement the observer design pattern
  20   *
  21   * @abstract
  22   * @subpackage    Base
  23   * @since        1.5
  24   */
  25  class JObserver extends JObject
  26  {
  27  
  28      /**
  29       * Event object to observe
  30       *
  31       * @access private
  32       * @var object
  33       */
  34      var $_subject = null;
  35  
  36      /**
  37       * Constructor
  38       */
  39  	function __construct(& $subject)
  40      {
  41          // Register the observer ($this) so we can be notified
  42          $subject->attach($this);
  43  
  44          // Set the subject to observe
  45          $this->_subject = & $subject;
  46      }
  47  
  48      /**
  49       * Method to update the state of observable objects
  50       *
  51       * @abstract Implement in child classes
  52       * @access public
  53       * @return mixed
  54       */
  55  	function update() {
  56          return JError::raiseError('9', 'JObserver::update: Method not implemented', 'This method should be implemented in a child class');
  57      }
  58  }