Firebase删除观察员 [英] Firebase removing observers

问题描述

在我的代码中移除Firebase观察者时遇到问题。以下是结构细分：

  var ref = Firebase（url：https://MY-APP.firebaseio.com /）
 var handle = UInt？ 
 
覆盖func viewDidLoad（）{
 handle = ref.observeEventType（.ChildChanged，withBlock：{
 
 
 //快照数据
 
 
 
重写func viewWillDisappear（animated：Bool）{
 if handle！= nil {
 println（Remove the handle） 
 ref.removeObserverWithHandle（handle！）
} 
} 
  

现在当我离开viewcontroller的时候，我看到Remove the handle被打印出来，但是当我返回到viewcontroller的时候，我的观察者每次被调用两次，当我离开并且再次返回的时候，它被调用了三次。是不是被删除的观察者？

我也在后面调用 ref.setValue（some value）代码，这可能与它有什么关系吗？
解决方案

原以为我有这个错误，但实际上我试图删除观察者的错误引用。

ORIGINAL CODE：
$ b

  let ref：FIRDatabaseReference = FIRDatabase.database（）。reference（）
 VAR childAddedHandles：[字符串：FIRDatabaseHandle] = [：] 
 
 FUNC observeFeedbackForUser（用户ID：字符串）{
如果childAddedHandles [用户id] ==零{//检查是否观察者已存在
 
 //注意： - 错误是由于我将.child（userId）添加到我的引用而引起的，而
 //在调用移除观察者时不引起。 
 
 childAddedHandles [用户id] = ref.child（用户id）.observeEventType（.ChildAdded）{
 [自弱（快照：FIRDataSnapshot）在
 
要是让post = snapshot.value as？ [String：AnyObject]，
 let likes = post [likes] as？ Int在哪里，喜欢> 0 {
 
 self？.receivedFeedback（snapshot.key，forUserId：userId）
} 
} 
} 
} 
 
 FUNC stopObservingUser（用户名：字符串）{
 //这不起作用
 
后卫让CAH = childAddedHandles.removeValueForKey（用户ID）否则{
打印（ 未观察用户 ）
返回
} 
 
 //错误！我没有将.child（userId）添加到我的引用
 ref.removeObserverWithHandle（cah）
} 
  

FIXED CODE：

pre $ func stopObservingUser（userId：String）{
//这个工作

警卫let cah = childAddedHandles.removeValueForKey（userId）else {
print（Not observing user）
return
}

/ / add .child（userId）here
ref.child（userId）.removeObserverWithHandle（cah）
}

I have a problem removing a Firebase observer in my code. Here's a breakdown of the structure:

var ref = Firebase(url:"https://MY-APP.firebaseio.com/")
var handle = UInt?

override func viewDidLoad() {
    handle = ref.observeEventType(.ChildChanged, withBlock: {
        snapshot in

        //Do something with the data
    }
}

override func viewWillDisappear(animated: Bool) {
    if handle != nil {
        println("Removed the handle")
        ref.removeObserverWithHandle(handle!)
    }
}

Now when I leave the viewcontroller, I see that "Removed the handle" is printed, but when I return to the viewcontroller, my observer is called twice for each event. When I leave and return again, it's called three times. Etc. Why is the observer not being removed?

I do also call ref.setValue("some value") later in the code, could this have anything to do with it?

解决方案

Thought I was having this bug but in reality I was trying to remove observers on the wrong reference.

ORIGINAL CODE:

let ref: FIRDatabaseReference = FIRDatabase.database().reference()
var childAddedHandles: [String:FIRDatabaseHandle] = [:]

func observeFeedbackForUser(userId: String) {
    if childAddedHandles[userId] == nil { // Check if observer already exists

        // NOTE: - Error is caused because I add .child(userId) to my reference and
        //     do not when I call to remove the observer.

        childAddedHandles[userId] = ref.child(userId).observeEventType(.ChildAdded) { 
            [weak self] (snapshot: FIRDataSnapshot) in

            if let post = snapshot.value as? [String:AnyObject],
               let likes = post["likes"] as? Int where likes > 0 {             

                self?.receivedFeedback(snapshot.key, forUserId: userId)          
            }
        }
    }
}

func stopObservingUser(userId: String) {
    // THIS DOES NOT WORK

    guard let cah = childAddedHandles.removeValueForKey(userId) else {
        print("Not observing user")
        return
    }

    // Error! I did not add .child(userId) to my reference
    ref.removeObserverWithHandle(cah)
}

FIXED CODE:

func stopObservingUser(userId: String) {
    // THIS WORKS

    guard let cah = childAddedHandles.removeValueForKey(userId) else {
        print("Not observing user")
        return
    }

    // Add .child(userId) here
    ref.child(userId).removeObserverWithHandle(cah)
}

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