/**
 * Constructor
 *
 * @param   DatabaseDriver  $db  Database driver object.
 *
 * @since   1.7.0
 */
public function __construct(DatabaseDriver $db)
{
    parent::__construct('#__extensions', 'extension_id', $db);
    // Set the alias since the column is called enabled
    $this->setColumnAlias('published', 'enabled');
}