Firebase 查询排序无法正常工作 [英] Firebase query ordering not working properly

问题描述

基本上我过去一周一直在使用 Firebase，最近我偶然发现了queryOrderedByChild()"，据我所知 - 允许您对 Firebase 中的数据进行排序.但是，我似乎没有得到正确的结果.我的 Firebase 数据如下所示:

Basically I have played with Firebase for the past week, and I recently stumbled upon the 'queryOrderedByChild()' that as far as I know - allows you to sort data in firebase. However, I seem to not get the proper results. My Firebase data looks like this:

{
  "names" : {
    "-KHVUwXdVPHmrO_O5kil" : {
      "id" : "0",
      "name" : "Jeff"
    },
    "-KHVV7lCeac0cZNMi9fq" : {
      "id" : "3",
      "name" : "Stig"
    },
    "-KHVVCjXgl0XxasVOHF1" : {
      "id" : "13",
      "name" : "Ali"
    },
    "-KHVVJtyUO-yJZiompJO" : {
      "id" : "7",
      "name" : "Hannah"
    },
    "-KHVVR8tMSO1Oh7R8tR1" : {
      "id" : "2",
      "name" : "Amanda"
    }
  }
}

，我的代码是这样的:

ref.childByAppendingPath("names")
   .queryOrderedByChild("id")
   .observeEventType(.ChildAdded) { (snapshot:FDataSnapshot!) in
       if let myID = snapshot.value["id"] as? String {
           print(myID)
       }

输出仍然是随机顺序，显示:0, 2,7,1,8,4 - 这不应该是数字吗?我究竟做错了什么?我怎样才能对它进行排序，使它得到升序或降序的数字?

The output is still in a random order, displaying: 0, 2,7,1,8,4 - Isn't this supposed to be numeric? What am I doing wrong? How can I sort it so it get's numeric either ascending or descending?

推荐答案

您说您是按数字排序，但您的 id 属性值存储为字符串.

You say that you're ordering by a number, but the value of your id property is stored as a string.

由于您将它们存储为字符串，它们将按词典顺序返回.

Since you're storing them as a string, they will be returned in lexicographical order.

如果您希望它们按数字顺序排列，则应将它们存储为数字

If you want them to be in numerical order, you should store them as numbers

"-KHVUwXdVPHmrO_O5kil" : {
  "id" : 0,
  "name" : "Jeff"
},

或者，您可以将 id 存储为以零填充的字符串:

Alternatively, you could store the ids as zero-padded strings:

{
  "names" : {
    "-KHVUwXdVPHmrO_O5kil" : {
      "id" : "0000",
      "name" : "Jeff"
    },
    "-KHVV7lCeac0cZNMi9fq" : {
      "id" : "0003",
      "name" : "Stig"
    },
    "-KHVVCjXgl0XxasVOHF1" : {
      "id" : "0013",
      "name" : "Ali"
    },
    "-KHVVJtyUO-yJZiompJO" : {
      "id" : "0007",
      "name" : "Hannah"
    },
    "-KHVVR8tMSO1Oh7R8tR1" : {
      "id" : "0002",
      "name" : "Amanda"
    }
  }
}

由于字符串的长度都相同，它们将按正确的顺序排序.但是你必须决定后一种解决方案中字符串/最大id值的长度，所以看起来更糟.

Since the strings are all the same length, they will be sorted in the correct order. But you'll have to decide on the length of the string/maximum id value in the latter solution, so it seems worse.

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