我想动态的在params里添加appid

[YLF]

WxPay::Service.invoke_unifiedorder params, {appid: brand.wechat_setting.wechat_appid }

返回

            "appId": null,
            "package": "prepay_id=wx102058425105161d3fef8d623853761149",
            "nonceStr": "ReAHJSELQGA5QjiX",
            "timeStamp": "1525957122",
            "signType": "MD5",
            "paySign": "9EE737772D15613015BB74B12588F599"

好像这样添加不进去，导致签名是错误的，添加mch_id或者key都是可以的
有空的话可以回答一下我吗？十分感谢