Question

我有多个帖子，每个帖子都有自己的评论。我想查询按时间戳排序的所有帖子。我试过了：

let query = Firebase(url: path)
let query.queryOrderedByChild("commentDate").observeEventType(.ChildAdded)
 { (queryResponse, cancelBlock) { ....

“commentDate”是服务器上的整数。在此查询中，我只获得第一个对象

let query = Firebase(url: path)
query.queryOrderedByChild("commentDate").queryLimitedToFirst(100).observeEventType(.ChildAdded) { (queryResponse, cancelBlock) { ...

我也只得到第一个对象...... 我目前的唯一解决方案是查询所有：

 query.queryOrderedByChild("commentDate").observeEventType(.Value) { (queryResponse, cancelBlock) in ...

但是使用这个我必须在向用户显示之前对数组进行排序。

我有什么想法可以让它们在服务器上排序？

修改火基数据的表示：

{
  "-KGRZmSIDXz5hHkelthQ" : {
    "something1" : "783151",
    "something2" : "21",
    "something3" : "wjeicisje ejej",
    "comments" : "",
  },
  "-KGRa5skGzA1GAG09Lno" : {
    "something1" : "783151",
    "something2" : "21",
    "something3" : "wjeicisje ejej",
    "comments" : "",
  },
  "-KGVr-tti1zr1M1QLlHL" : {
    "something1" : "783151",
    "something2" : "21",
    "something3" : "wjeicisje ejej",
    "comments" : {
      "-KGX1_rFSBLmQJ7QzCRc" : {
        "commentBody" : "something",
        "commentDate" : 1.461933727259896E9,
        "commentOwnerImageView" : "something",
        "commentOwnerName" : "something"
      },
      "-KGX1r5Lnhv9YbQre6as" : {
        "commentBody" : "something",
        "commentDate" : 1.461933797884702E9,
        "commentOwnerImageView" : "something",
        "commentOwnerName" : "something"
      },
      "-KGXVGKA0SYm-vRs6zsv" : {
          "commentBody" : "something",
        "commentDate" : 1.461941507496439E9,
        "commentOwnerImageView" : "something",
        "commentOwnerName" : "something"
      },
    },
  }
}

Answer 1

您的数据结构看起来很好，因此简单的查询将返回您想要的结果

let commentsRef = ref.childByAppendingPath("-KGVr-tti1zr1M1QLlHL/comments")

commentsRef.queryOrderedByChild("commentDate").observeEventType(.ChildAdded, withBlock: {
  snapshot in

  let nodeData = snapshot.value
  print(nodeData!)

})

以上将返回每个子节点，按正确的顺序一次返回一个。

如果你有少量的节点，你可以一次读取它们并迭代快照。孩子这样

usersRef.queryOrderedByChild("commentDate").observeEventType(.Value, withBlock: {
  snapshot in

  for child in snapshot.children {
    print(child)
  }

})

以上两个都将打印出commentDate

命令的每个评论节点

只有当您有兴趣检索每篇文章中的评论时，上述内容才有效。如果没有，您需要更改Firebase结构并将注释移动到单独的节点，如此

posts
   post_01
   post_02
   etc

和一个单独的注释节点，它指的是注释所属的帖子。由于您要查询post_02的评论，并希望它们通过commentDate排序，请将帖子编号和日期合并为一个孩子。

comments
   "-KGX1_rFSBLmQJ7QzCRc" : {
     "for_post_and_commentDate": "post_02_1.461933727259896E9",
     "commentBody" : "something",
     "commentOwnerImageView" : "something",
     "commentOwnerName" : "something"
   },
   "-KGX1r5Lnhv9YbQre6as" : {
     "for_post_and_commentDate": "post_02_1.461933797884702E9",
     "commentBody" : "something",
     "commentOwnerImageView" : "something",
     "commentOwnerName" : "something"
     },

然后修改查询

usersRef.queryOrderedByChild("for_post_and_commentDate")
   queryStartingAtValue("post_02_0").queryEndingAtValue("post_02_xxx").observeEventType(.Value, withBlock: {

你必须弄清楚你的commentDate格式，因为如果它们被存储起来更容易制作开始和结束时间戳：20160430100621作为yyyymmddhhmmss格式，那么你的时间戳可以这样查询：

starting: post_02_0
ending: post_02_99999999999999

这也使您可以灵活地查询昨天或上周发生的post_02的评论。

Answer 2

如果你知道整个路径（例如dimensions/length），Firebase可以查询嵌套的子节点。它无法处理每个子项下该路径中的动态元素（如$commentid/commentDate）。

实现此功能的唯一方法是将必要的数据提升到可以查询的级别。例如，如果您跟踪每篇博文的lastCommentDate：

{
  "-KGRZmSIDXz5hHkelthQ" : {
    "something1" : "783151",
    "something2" : "21",
    "something3" : "wjeicisje ejej",
    "comments" : "",
  },
  "-KGRa5skGzA1GAG09Lno" : {
    "something1" : "783151",
    "something2" : "21",
    "something3" : "wjeicisje ejej",
    "comments" : "",
  },
  "-KGVr-tti1zr1M1QLlHL" : {
    "something1" : "783151",
    "something2" : "21",
    "something3" : "wjeicisje ejej",
    "firstCommentDate": 1.461933727259896E9,
    "lastCommentDate": 1.461941507496439E9,
    "comments" : {
      "-KGX1_rFSBLmQJ7QzCRc" : {
        "commentBody" : "something",
        "commentDate" : 1.461933727259896E9,
        "commentOwnerImageView" : "something",
        "commentOwnerName" : "something"
      },
      "-KGX1r5Lnhv9YbQre6as" : {
        "commentBody" : "something",
        "commentDate" : 1.461933797884702E9,
        "commentOwnerImageView" : "something",
        "commentOwnerName" : "something"
      },
      "-KGXVGKA0SYm-vRs6zsv" : {
          "commentBody" : "something",
        "commentDate" : 1.461941507496439E9,
        "commentOwnerImageView" : "something",
        "commentOwnerName" : "something"
      },
    },
  }
}

使用此结构，您可以按其上次评论日期查询博客帖子：

ref.orderByChild('lastCommentDate').limitToLast(10).on(...

Firebase查询订单

2 个答案: