youxiangjie/application/api/model/CommodityModel.php

<?php
namespace app\api\model;
use think\Model;

class CommodityModel extends Model
{
    protected $name = "commodity";
    protected $resultSetType = 'collection';
    public function parameter () {
        return $this->hasMany('parameter','c_id','c_id');
    }
    public function buycar () {
        return $this->belongsTo('BuycarModel','c_id','c_id');
    }
}