Feed 在刷新或重启后丢失所有数据

Question

我正在使用 cloudkit 创建一个类似 Twitter 的应用程序，在我刷新或重新启动该应用程序之前一切正常。没有错误，但提要变空并丢失所有数据。我没有尝试查看多人使用该应用程序时会发生什么。

class SweetsTableViewController: UITableViewController {
    var sweets = [CKRecord]()
    var refresh: UIRefreshControl!
    override func viewDidLoad() {
        super.viewDidLoad()
        refresh = UIRefreshControl()
        refresh.attributedTitle = NSAttributedString(string: "Pull to Refresh")
        refresh.addTarget(self, action: "loadData", forControlEvents: .ValueChanged)
        self.tableView.addSubview(refresh)
        loadData()
    }
    func loadData()
    {
        sweets = [CKRecord]()
        let publicData = CKContainer.defaultContainer().publicCloudDatabase
        let query = CKQuery(recordType: "Beam", predicate: NSPredicate(format: "TRUEPREDICATE", argumentArray:nil))
        query.sortDescriptors = [NSSortDescriptor(key:"creationDate", ascending: false)]
        publicData.performQuery(query, inZoneWithID: nil) { (results: [CKRecord]?, error: NSError?) -> Void in
            if let sweets = results
            {
                self.sweets = sweets
                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.tableView.reloadData()
                    self.refresh.endRefreshing()
                })
            }
        }
    }
    @IBAction func sendSweet(sender: AnyObject)
    {
        let alert = UIAlertController(title: "New Beam", message: "Type a Beam", preferredStyle: .Alert)
        alert.addTextFieldWithConfigurationHandler { (textField: UITextField) in
            textField.placeholder = "Your Beam"
        }
        alert.addAction(UIAlertAction(title: "Send", style: .Default, handler: {(action: UIAlertAction) -> Void in
            let textField = alert.textFields!.first!
            if textField.text != ""
            {
                let newBeam = CKRecord(recordType: "Beam")
                newBeam["content"] = textField.text
                let publicData = CKContainer.defaultContainer().publicCloudDatabase
                publicData.saveRecord(newBeam, completionHandler: {(record:CKRecord?, error: NSError?) -> Void in
                    if error == nil
                    {
                        dispatch_async(dispatch_get_main_queue(), {() -> Void in
                            print("Beam saved")
                            self.tableView.beginUpdates()
                            self.sweets.insert(newBeam, atIndex: 0)
                            let indexPath = NSIndexPath(forRow: 0, inSection: 0)
                            self.tableView.insertRowsAtIndexPaths([indexPath], withRowAnimation: .Top)
                            self.tableView.endUpdates()
                        })
                    }else{
                        print(error)
                    }
                })
            }
        }))
        alert.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: nil))
        self.presentViewController(alert, animated: true, completion: nil)
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return 1
    }
    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return sweets.count
    }
    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
        if sweets.count == 0
        {
            return cell
        }
        let sweet = sweets[indexPath.row]
        if let sweetContent = sweet["content"] as? String
        {
            let dateFormat = NSDateFormatter()
            dateFormat.dateFormat = "MM/dd/yyyy"
            let dateString = dateFormat.stringFromDate(sweet.creationDate!)
            cell.textLabel?.text = sweetContent
            cell.detailTextLabel?.text = dateString
        }
        return cell
    }

Answer 1

写入 CloudKit 数据库的记录并不总是在查询中立即返回 (CKQuery/CKQueryOperation)。

Query indexes are updated asynchronously so they are not guaranteed to be current. If you query for records that you recently changed and not allow enough time for those changes to be processed, the query results may be incorrect. The results may not contain the correct records and the records may be out of order.

参考：CKQueryOperation

您可能想要调查使用 CKSubscription / CKQuerySubscription (iOS 10+) 在数据库发生更改时接收通知。

Feed 在刷新或重启后丢失所有数据

Feed loses all data after refresh or restart

refresh

ios

swift

cloudkit

ckrecord