firebase实时数据库使用angularfire 2更新过滤器后的条目

"orders" : {
    "-LM5p4tl7Og_PMJOspZ-" : {
      "customer" : {
        "_name" : "Vik Kumar",
        "_uid" : "oSEYj0zrkhPCk9r7uwyOOkHcqe53"
      },
      "order" : {
        "_orderNumber" : "VikKumar-26954",
        "_orderStatus" : "Pending",
        "_orderTotal" : 500,
      }
    },
    "-LM5s1wRCvqWA1vsZONy" : {
      "customer" : {
        "_name" : "Vik Kumar",
        "_uid" : "oSEYj0zrkhPCk9r7uwyOOkHcqe53"
      },
      "order" : {
        "_orderNumber" : "VikKumar-11423",
        "_orderStatus" : "Pending",
        "_orderTotal" : 500,
      }
    },
    "-LM5sOHzjLeqFGFleMxq" : {
      "customer" : {
        "_name" : "Vik Kumar",
        "_uid" : "oSEYj0zrkhPCk9r7uwyOOkHcqe53"
      },
      "order" : {
        "_orderNumber" : "VikKumar-63772",
        "_orderStatus" : "Pending",
        "_orderTotal" : 500,
      }
    }
}

我在我的ionic应用程序中使用angularfire2,并过滤以下几个订单:

getPendingOrders(dateStr:string){
    return new Promise((resolve, reject) =>
      {
        this.db.list('orders',
                     ref =>  ref.orderByChild("order/_date").equalTo(dateStr)
       ).valueChanges().subscribe(
        res => {
          resolve(res)
        },
        err => {
          console.log(err)
          reject(err)
        }
      )
      })
  }

以上查询给我的答复如下

[{"customer": {}, "order": {}}, {"customer": {}, "order": {}}]

我可以在UI中呈现它,我希望最终用户能够更新属性“\u orderStatus”的值。问题在于我查询数据的方式,我丢失了识别特定对象的键来更新它。请告知