public function next()
    {
        $cls  = $this->_cls;
        $data = $this->_getCurrentData();

        if (!$data) {
            $this->_curval = null;
            return $this->_curval;
        } else {
            ++$this->_count;
            $this->_curval = $data;
            return new $this->_cls($this->_curval);
        }
    }