ThinkPHP3.0的parseFieldsMap有关问题

    protected $_map = array(
        'id' => 'uid',
        'name' => 'uname',
    );

        $model = M('Demo');
        $list = $model -> select();
        print_r($list);
        $list = $model -> parseFieldsMap($list);
        echo '

';
        print_r($list);

    /**
     +----------------------
     * 处理字段映射
     +----------------------
     * @access public
     +----------------------
     * @param array $data 当前数据
     * @param integer $type 类型 0 写入 1 读取
     +----------------------
     * @return array
     +----------------------
     */
    public function parseFieldsMap($data,$type=1) {
        // 检查字段映射
        if(!empty($this->_map)) {
            foreach ($this->_map as $key=>$val){
                if($type==1) { // 读取
                    if(isset($data[$val])) {
                        $data[$key] =   $data[$val];
                        unset($data[$val]);
                    }
                }else{
                    if(isset($data[$key])) {
                        $data[$val] =   $data[$key];
                        unset($data[$key]);
                    }
                }
            }
        }
        return $data;
    }