不正确的Firebase数据返回

Question

我有以下Swift & Firebase代码按预期方式返回数据（最初），但如果数据被其他用户更改并且当前用户返回到表中，则会显示旧数据。 如果用户出去并返回到表中，然后显示正确的数据，它只会更新新数据。

这是因为如果该数据被缓存，但我已经持续禁用）：

import UIKit 
import Firebase 

class Agent_NewRequests: UITableViewController { 

    let custom = custom() 
    var dbConnector = FIRDatabase.database().reference() 

    var userID:String! 
    var searchResults = [agentNewRequests]() 
    var requestID:String! 

    var loadingOverlay = LoadingOverlay() 


    override func viewDidLoad() { 
     super.viewDidLoad() 
    } 

    override func viewWillAppear(animated: Bool) { 
     self.searchResults.removeAll(keepCapacity: false) 
     FIRAuth.auth()!.addAuthStateDidChangeListener() { (auth, user) in 
      if user != nil { 
       // user authenticated 
       self.userID = user!.uid 
       self.retrieveRequests() 
      } else { 
       // No user is signed in 
       self.custom.showLogin(self.self) 
      } 
     } 
    } 

    override func viewWillDisappear(animated: Bool) { 
     dbConnector.removeAllObservers() 
    } 

    func retrieveRequests() { 
     if self.userID == "" { 
      loadingOverlay.hideOverlayView() 
      // todo - show error 
      return 
     } 

     loadingOverlay.showOverlay(self.view) 
     var timeLastUpdated = "" 
     self.searchResults.removeAll(keepCapacity: false) 

     let userRef = dbConnector.child("requests/\(self.userID)") 
     userRef.queryEqualToValue("Submitted", childKey: "status") 
     userRef.observeSingleEventOfType(.ChildAdded, withBlock: { snapshot in 
      guard snapshot.exists() else { 
       // No data found, handle error otherwise will crash 
       self.checkTable() 
       self.loadingOverlay.hideOverlayView() 
       return 
      } 

      if let _:String = snapshot.value!["status"] as? String { } else { 
       self.checkTable() 
       self.loadingOverlay.hideOverlayView() 
       return 
      } 

      let status = snapshot.value!["status"] as! String 

      if status != "Submitted" { 
       self.checkTable() 
       return 
      } 

      let key = snapshot.key as String 
      let tenantID = snapshot.value!["tenant_id"] as! String 
      let address = snapshot.value!["address"] as! String 
      let desc = snapshot.value!["description"] as! String 
      let timeUpdate:Int = snapshot.value!["time_updated"] as! Int 
      let priority = snapshot.value!["priority"] as! Int 

      let dateFormat = NSDateFormatter() 
      dateFormat.dateStyle = NSDateFormatterStyle.LongStyle 
      dateFormat.timeStyle = NSDateFormatterStyle.ShortStyle 

      if timeUpdate == 0 { // if it has never been updated, use time created instead for lastupdated 
       let cTimeInterval = snapshot.value!["time_created"] as? NSTimeInterval 
       let updateTime = NSDate(timeIntervalSince1970: cTimeInterval!/1000) 
       timeLastUpdated = dateFormat.stringFromDate(updateTime) 
      } else { 
       let uTimeInterval = snapshot.value!["time_updated"] as? NSTimeInterval 
       let updateTime = NSDate(timeIntervalSince1970: uTimeInterval!/1000) 
       timeLastUpdated = dateFormat.stringFromDate(updateTime) 

      } 
      var imgData:String = "" 

      self.searchResults += [agentNewRequests(requestID: key, tenantID: tenantID, address: address, description: desc, lastUpdated: timeLastUpdated, mediaData: mediaData, priority: priority)] 
      dispatch_async(dispatch_get_main_queue()){ 
       self.checkTable() 
      } 
     }) { error in 
      print(error.description) 
      self.loadingOverlay.hideOverlayView() 
     } 
    } 


    func checkTable() { 
     if (self.searchResults.count > 0) { 
      self.searchResults = self.searchResults.reverse() 
      self.tableView.reloadData() 
      self.loadingOverlay.hideOverlayView() 
      // remove any previous signs of errorMessageLabel 
      self.tableView.backgroundView = nil 
      self.tableView.separatorColor = custom.UIColorFromRGB(0x574987, alphaValue: 1) 
      self.tableView.separatorStyle = UITableViewCellSeparatorStyle.SingleLine 
     } else { 
      self.tableView.reloadData() 
      self.loadingOverlay.hideOverlayView() 
      // Display a message that the table is empty 
      let errorMessageLabel = UILabel() 
      errorMessageLabel.frame = CGRectMake(0, 0, self.tableView.bounds.width, (self.tableView.bounds.height + 100)) 
      errorMessageLabel.text = "No new requests found" 
      errorMessageLabel.numberOfLines = 1 
      errorMessageLabel.textColor = UIColor.blackColor() 
      errorMessageLabel.textAlignment = NSTextAlignment.Center 
      errorMessageLabel.sizeToFit() 
      self.tableView.backgroundView = errorMessageLabel 
      self.tableView.separatorColor = UIColor.clearColor() 
      self.tableView.separatorStyle = UITableViewCellSeparatorStyle.SingleLine 
     } 
    } 

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { 

     let cell:Agent_NewRequests_Cell = self.tableView.dequeueReusableCellWithIdentifier("requestCell") 
      as! Agent_NewRequests_Cell 
     cell.idLabel.text = searchResults[indexPath.row].description 
     cell.updatedLabel.text = searchResults[indexPath.row].lastUpdated 
     cell.addressLabel.text = searchResults[indexPath.row].address 

     return cell 
    } 

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 
     return searchResults.count 
    } 

    override func numberOfSectionsInTableView(tableView: UITableView) -> Int { 
     return 1 
    } 

    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) { 
     requestID = searchResults[indexPath.row].requestID 
     self.performSegueWithIdentifier("newToRequestCard", sender: indexPath); 
    } 

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) { 
     if (segue.identifier == "newToRequestCard") { 
      let requestCard = segue.destinationViewController as! Agent_Request_Card; 
      requestCard.toPass_requestID = self.requestID 
      requestCard.toPass_agentID = self.userID 
     } 
    } 

    override func didReceiveMemoryWarning() { 
     super.didReceiveMemoryWarning() 
    } 
} 

如果我改变它从.ObserveSingleEventOfType到.ObserveEventType它工作正常但是...如果数据在其他地方删除没有其他数据，UI只是坐在监听更新，我不想这样，我需要告诉用户没有UI更新的数据（这从来不会发生）

Answer 1

使用ObserveEventType而不是ObserveSingleEventOfType并检查数据是否存在。如果不是，则用消息更新UI。如果是，继续正常。