Question

我在firebase中有一些数据，我试图按时间戳组织。我已将此代码合并到cellForRowAt

中

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        if let seconds = post["pub_time"] as? Double {
            let timeStampDate = NSDate(timeIntervalSince1970: seconds/1000)
            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "MM/dd/yyyy"
            let formating = timeStampDate as Date


        let timeAgo = timeAgoSinceDate(formating)

            cell.Time.text = timeAgo

            posts.sort(by: { $0.timeStampDate.compare($1.timeStampDate) == .orderedAscending })


            }

但在posts.sort(by: { $0.timeStampDate.compare($1.timeStampDate) == .orderedAscending })我一直收到错误表达式类型bool是不明确的，没有更多上下文，我不确定我做错了什么

这或多或少是我的视图控制器的样子

    var posts = NSMutableArray()

    func loadData(){
        Database.database().reference().child("main").child("posts").queryOrdered(byChild: "pub_time").observeSingleEvent(of: .value, with: { snapshot in

                if let postsDictionary = snapshot .value as? [String: AnyObject] {
                    for post in postsDictionary {
                        posts.add(post.value)

                    }
                    self.TableView.reloadData()
                }

         })
    }

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        // Configure the cell...
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cells", for: indexPath) as! FeedTableViewCell

        //Configure the cell
let post = posts[indexPath.row] as! [String: AnyObject]
cell.Title.text = post["title"] as? String
 if let seconds = post["pub_time"] as? Double {
            let timeStampDate = NSDate(timeIntervalSince1970: seconds/1000)
            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "MM/dd/yyyy"
            let formating = timeStampDate as Date


        let timeAgo = timeAgoSinceDate(formating)

            cell.Time.text = timeAgo



            }

        return cell
    }

Answer 1

这里是如何对一组对象进行排序的; acending是默认顺序。

假设您有像这样的PostClass

class PostClass {
   var timeStampDate = "" //assume the timestamps are yyyyMMddhhmmss strings
   var post = ""
}

并将它们存储在posts数组中

var posts = [PostClass]()

对数组中的posts对象进行排序的代码是：

posts.sort(by: {$0.timeStampDate < $1.timeStampDate })

话虽如此，您可能需要考虑让Firebase执行繁重的工作并为您订购数据，以便以正确的顺序在快照中显示。

假设您有Firebase结构

posts
   post_0
     post: "A post about some stuff"
     timestamp: "2"
   post_1
     post: "Posting about how to post"
     timestamp: "3"
   post_2
     post: "The post for you"
     timestamp: "1"

我们要加载帖子，按时间戳排序

let postsRef = self.ref.child("posts")
let postQuery = postsRef.queryOrdered(byChild: "timestamp")
postQuery.observeSingleEvent(of: .value, with: { snapshot in
    for child in snapshot.children {
        let snap = child as! DataSnapshot
        let dict = snap.value as! [String: Any]
        let post = dict["post"] as! String
        let ts = dict["timestamp"] as! Int
        print(ts, post)
    }
})

和输出

1 The post for you
2 Posting about how to post
3 A post about some stuff

对于这个例子，我使用1,2,3作为我的时间戳，但yyyyMMddhhmmss（20180618101000）格式也可以使用，并提供人类可读的正确排序。

按时间戳组织firebase数据

1 个答案: