Method __construct

/**
 * Constructor
 *
 * @param   DatabaseDriver  $db  A database connector object
 *
 * @since   1.5
 */
public function __construct(DatabaseDriver $db)
{
    $this->typeAlias = 'com_content.article';
    parent::__construct('#__content', 'id', $db);
    // Set the alias since the column is called state
    $this->setColumnAlias('published', 'state');
}