/节点列表
    public function node(){
        
        if(!$node = S('node_list')){
            $field = array('id', 'name', 'title', 'pid');
            $node = M('node')->field($field)->order('sort')->select();
            $node = node_merge($node);
            S('node_list', $node, 3600);    //将节点列表缓存1小时
        }
        $this->node = $node;
        $this->display();
    }