public function getIds($key = null)
    {
        if (!isset($this->_mixer->__ids)) {
            $this->_mixer->__ids = array();
        }

        $prop = $key ? $key : 'id';
        $key = $key ? $key.'_ids' : 'ids';

        if (!isset($this->_mixer->__ids[$key])) {
            $columns = $this->getRowData();

            if (!empty($columns[$key])) {
                $ids = explode(',', $columns[$key]);
            } else {
                $ids = isset($this->$prop) ? ($prop == 'id' ? array($this->id) : array($this->$prop->id)) : array();
            }

            $this->_mixer->__ids[$key] = $ids;
        }

        return $this->_mixer->__ids[$key];
    }