在更新後在Firebase中查找項目的舊值

Question

我正在製作一個簡單的應用程序，使用Firebase執行CRUD工作 - 添加，更新和刪除。我已經完成了所有這些，除了我有一個更新問題的事實。

我可以在更新子值時獲得對正確用戶的引用，並使其在Firebase控制檯中成功更新。這是我用的代碼：

let ref = FIRDatabase.database().reference().child("Users") 
    ref.observeEventType(.ChildAdded, withBlock: { (snapshot) in 

     guard let dictionary = snapshot.value as? [String:AnyObject] else { return } 

     if self.firstNameField.text == dictionary["firstname"] as? String 
     { 
      if let lastname = dictionary["lastname"] 
      { 
       print("Here is the lastname of the current person \(lastname)") 

       guard let firstname = self.firstNameField.text, lastname = self.lastNameField.text, dateOfBirth = self.dateOfBirthField.text, zipcode = Int(self.zipcodeField.text!) else 
       { 
        print("Form not valid") 
        return 
       } 

       let properties: [String: AnyObject] = ["firstname": firstname, "lastname": lastname, "Date of Birth": dateOfBirth, "Zipcode": zipcode] 

       let currentKey = snapshot.key 
       ref.child(currentKey).updateChildValues(properties, withCompletionBlock: { (error, ref) in 

        if error != nil 
        { 
         print("We have an error updating the data \(error)") 
        } 

        print("We were able to update the entry in the reference \(ref)") 

       }) 
      } 
     } 

    }, withCancelBlock: nil) 

我的問題是TableViewController不是隻要我解僱EditViewController更新正確的索引。 tableview.reloadData（）方法對此不起作用，所以我想我需要在我的ChildChanged方法中修復它。下面是該代碼：

ref.observeEventType(.ChildChanged, withBlock: { (snapshot) in 

     print("One of the entries were changed so we're reloading the table view") 

     if let firstname = snapshot.value?.objectForKey("firstname"), lastname = snapshot.value?.objectForKey("lastname") 
     { 
      let fullname = "\(firstname) \(lastname)" 
      self.names[I_Need_This_Index] = fullname 
      print(fullname) 

      dispatch_async(dispatch_get_main_queue()) 
      { 
       self.tableView.reloadData() 
      } 
     } 

    }, withCancelBlock: nil) 

上面的代碼是在一個稱爲observePeople（）方法，它是viewDidLoad方法期間調用。 observePeople（）方法處理了ChildAdded，ChildRemoved和ChildChanged通知。

如何正確導航到舊索引並將舊值更改爲新值，以便表視圖正確更新？

Answer 1

這裏有一個臨時的解決方案，我有一個只能使用一次，然後後不工作：

我創建一個名爲「ogFullName」一個全局字符串變量，並將其設置爲全稱中的孩子添加的代碼。然後在我的孩子改變代碼，我設置「ogFullName」我試圖改變的元素的索引。這是一個有點我很難言傳，所以這裏是代碼：

var ogFullname:String? 

func observePeople() 
{ 
    let ref = FIRDatabase.database().reference().child("Users") 
    ref.observeEventType(.ChildAdded, withBlock: 
    { (snapshot) in 

     if let firstname = snapshot.value?.objectForKey("firstname"), lastname = snapshot.value?.objectForKey("lastname") 
     { 
      let fullname = "\(firstname) \(lastname)" 
      self.ogFullname = fullname //the old name 
... 

而且在這裏我ChildChanged代碼：

ref.observeEventType(.ChildChanged, withBlock: { (snapshot) in 

     print("One of the entries were changed so we're reloading the table view") 

     if let firstname = snapshot.value?.objectForKey("firstname"), lastname = snapshot.value?.objectForKey("lastname") 
     { 
      let fullname = "\(firstname) \(lastname)" 
      if let ogname = self.ogFullname 
      { 
       if let originalIndex = self.names.indexOf(agnate) //finding the index of the unchanged name 
       { 
        self.names[originalIndex] = fullname //setting the old name to the changed one 
       } 

此解決方案僅按建築工作一次。之後，它繼續顯示控制檯上顯示的更新的相同行爲，但不是表視圖。