ios - 按降序时间过滤时向 Firebase 观察者添加新帖子

Question

因此，我有一个供用户发布的提要，并希望每个新提交的内容都位于我的 Collection View 的顶部。我使用此处显示的 UTC 时间的负值按时间降序对每个新帖子进行排序:How do you properly order data from Firebase chronologically 。

    "Posts" : {
      "-KHLOy5mOSq0SeB7GBXv" : {
           "timestamp" : "1476028495915",
           "descendStamp": "-1476028495915"
           "otherData": ""
       },
      "-KHLrapS0wbjqPP5ZSUY" : {
           "timestamp" : "1476028496102"
           "descendStamp" : "-1476028496102"
           "otherData": ""
       },

但是，每个新添加的实时帖子在最初加载时都会被放在底部。相信这是由于观察者仅异步加载新添加的子项而不会再次下载任何其他信息，这导致它忽略我的

    .queryOrderedByChild("descendStamp")

离开并返回 View 后，它会将最近添加的帖子正确组织到顶部。我是否需要客户端过滤才能实时将这些新帖子放在顶部？或者当新帖子出现时重新组织帖子顺序的最佳方法是什么？

    var posts = [PostModel]()

    let postQuery = ref.child("Posts").queryOrderedByChild("descendStamp")
        postQuery.observeEventType(.ChildAdded, withBlock: { (snap) in


            if snap.exists() {
                let postData = snap.value! as! [String: AnyObject]

                let post = PostModel()

                post.timestamp = postData["timestamp"] as? NSTimeInterval
                post.descendStamp = postData["descentStamp"] as? NSTimeInterval
                post.otherData = postData["otherData"] as? String

                self.posts.append(post)

                dispatch_async(dispatch_get_main_queue(), {
                    self.collectionView!.reloadData()
                })
            }

Answer 1

在更新 tableView 之前对数据源进行排序。

self.posts.sort(by: {$0.descendStamp > $1.descendStamp})

你的代码看起来像这样:-

var posts = [PostModel]()

let postQuery = ref.child("Posts").queryOrderedByChild("descendStamp")
    postQuery.observeEventType(.ChildAdded, withBlock: { (snap) in


        if snap.exists() {
            let postData = snap.value! as! [String: AnyObject]

            let post = PostModel()

            post.timestamp = postData["timestamp"] as? NSTimeInterval
            post.descendStamp = postData["descentStamp"] as? NSTimeInterval
            post.otherData = postData["otherData"] as? String

            self.posts.append(post)
            self.posts.sort(by: {$0.descendStamp > $1.descendStamp})

            dispatch_async(dispatch_get_main_queue(), {
                self.posts.sort(by: {$0.descendStamp > $1.descendStamp})
                self.collectionView!.reloadData()
            })
        }