codeigniter - php 新手 问题

model

    class Stock_model extends CI_Model{

        private $hsh;
        function __construct()
        {
            parent::__construct();
            $_ci = & get_instance();


            //$this->hsh = $_ci->load->database('hsh',TRUE);
            $hsh = $_ci->load->database('hsh',TRUE);
        }



        function  get_stock($goods_huo)
        {
            if(isset($goods_huo))
            {
                $hsh->where('item_huo',$goods_huo);
                $query =  $hsh->get('item_info');

                return $query->result_array();
                $query->free_result();

            }
        }
    }

报错

A PHP Error was encountered
Severity: Notice
Message:  Undefined variable: hsh
Filename: models/stock_model.php
Line Number: 22