ios - 如何使用 Firestore 订购数据以在 iOS 上显示

Question

我正在尝试按时间戳排序我的数据，但它似乎不起作用。我的 Feed 类在下面。有人可以看一下并告诉我发生了什么事吗？我相信问题出在 checkForUpdates() 函数中。我已尽一切努力让数据按时间戳排序。当我删除 loadData() 函数时，应用程序按时间戳顺序显示帖子，但新帖子始终位于 View 的末尾。

导入UIKit导入FirebaseFirestore

FeedVC 类:UITableViewController {

var db = Firestore.firestore()
var postArray = [Posts]()

override func viewDidLoad() {
    super.viewDidLoad()

    //db = Firestore.firestore()

//加载数据() //checkForUpdates()

}
   override func viewDidAppear(_ animated: Bool){
     checkForUpdates()
    loadData()



}

func loadData() {
    db.collection("posts").getDocuments() {
        querySnapshot, error in
        if let error = error {
            print("\(error.localizedDescription)")
        }else{
            self.postArray = querySnapshot!.documents.flatMap({Posts(dictionary: $0.data())})
            DispatchQueue.main.async {
                self.tableView.reloadData()
            }
        }
    }


}

func checkForUpdates() {
    db.collection("posts").order(by: "timeStamp", descending: true)
    .addSnapshotListener {
            querySnapshot, error in

            guard let snapshot = querySnapshot else {return}

            snapshot.documentChanges.forEach {
                diff in

                if diff.type == .added {
                    self.postArray.append(Posts(dictionary: diff.document.data())!)
                    DispatchQueue.main.async {
                        self.tableView.reloadData()
                    }
                }
            }

    }
}

@IBAction func composePost(_ sender: Any) {





    let composeAlert = UIAlertController(title: "New Post", message: "Enter your name and message", preferredStyle: .alert)

    composeAlert.addTextField { (textField:UITextField) in
        textField.placeholder = "Your name"
    }

    composeAlert.addTextField { (textField:UITextField) in
        textField.placeholder = "Your message"
    }

    composeAlert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))

    composeAlert.addAction(UIAlertAction(title: "Send", style: .default, handler: { (action:UIAlertAction) in do {


        if let name = composeAlert.textFields?.first?.text, let content = composeAlert.textFields?.last?.text {

            let newSweet = Posts(name: name, content: content, timeStamp: Timestamp())

            var ref:DocumentReference? = nil
            ref = self.db.collection("posts").addDocument(data: newSweet.dictionary) {
                error in

                if let error = error {
                    print("Error adding document: \(error.localizedDescription)")
                }else{
                    print("Document added with ID: \(ref!.documentID)")
                }

            }

        }
        }

    }))

    self.present(composeAlert, animated: true, completion: nil)


}



// MARK: - Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {

    return 1
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    return postArray.count
}


override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)

    let post = postArray[indexPath.row]

    cell.textLabel?.text = "\(post.name): \(post.content)"
    cell.detailTextLabel?.text = "\(post.timeStamp.dateValue())"

    return cell
}

}

Answer 1

加载数据时使用 order by:

chats.order(by: "createdTime", descending: false)