/**
  * Retrieve the singleton instance of this class.
  *
  * @return sfDoctrineFinderListener A sfDoctrineFinderListener implementation instance.
  */
 public static function getInstance()
 {
     if (!isset(self::$instance)) {
         $class = __CLASS__;
         self::$instance = new $class();
         if (sfConfig::get('sf_debug') && sfConfig::get('sf_logging_enabled')) {
             Doctrine_Manager::connection()->addListener(self::$instance);
         }
     }
     return self::$instance;
 }
 public function initialize($connection, $class, $alias)
 {
     $this->query = Doctrine_Query::create($connection)->from($class . ' ' . $alias);
     $this->queryListener = sfDoctrineFinderListener::getInstance();
     $this->aliases = array();
     if ($alias) {
         $this->addAlias($class, $alias);
     }
     $this->reinitWithClasses();
     $this->reinitWithColumns();
     return $this;
 }