Firebase database doesn't stop updating

Question

I was trying to update my Firebase database and I ran into this problem. Take a look at the following code snippet and the screenshot:

func saveRetrieveStoryID(completion: @escaping (Bool) -> Void) {

    let userID = Auth.auth().currentUser?.uid
    //Create a reference to the database
    let DBRef = Database.database().reference()

    let storyIDRef = DBRef.child("Story IDs").child(userID!)
    storyIDRef.observe(.value) { (snapshot) in

        for childOne in snapshot.children {
            print(childOne)
            if let childOneSnapshot = childOne as? DataSnapshot {

                storyIDKeyList.append(Int(childOneSnapshot.key)!)
                print(childOneSnapshot.key)
                completion(true)
            }
        }
        print(storyIDKeyList)
    }
}

What the code does is that it retrieves the key (-1) from the database and stores it inside a list (storyIDKeyList). Now take a look at the following code snippet:

saveRetrieveStoryID { (saved) in
    if saved {

        // Store the story ID in the user's story ID dict
        let storyIDRef = DBRef.child("Story IDs").child(userID!)
        let newStoryIDKey = storyIDKeyList.last! + 1

        storyIDs[String(newStoryIDKey)] = storyRef.key

        storyIDRef.updateChildValues(storyIDs, withCompletionBlock: { (error, ref) in
            if let error = error?.localizedDescription {
                print("Failed to update databse with error: ", error)
            }
        })
    }
}

This piece of code, takes the last item from the storyIDKeyList and adds 1 to it. Then this will be added to the storyIDs dictionary storyIDs[String(newStoryIDKey)] = storyRef.key and the database will be update with the new key and value. But the problem is that, the database keeps on updating and it doesn't stop until I stop running the code. Here is a picture of the resulting database:

Notice that all the values are the same. This following screenshot should be the expected outcome:

I just want to add one key/value to the database each time I run the code; I kind of know why this is happening but I'm finding it difficult to solve this problem.

Answer 1

After a lot of tries, I managed to find a solution to this problem.

Edit: I found a better solution, thanks to this answer: Android Firebase Database keeps updating value. Using observeSingleEvent() retrieves the data only once.

Here is the code (Better answer IMO):

func saveRetrieveStoryID(completion: @escaping (Bool) -> Void) {

    let userID = Auth.auth().currentUser?.uid

    let storyIDRef = DBRef.child("Story IDs").child(userID!)
    storyIDRef.observeSingleEvent(of: .value) { (snapshot) in

        for childOne in snapshot.children {

            if let childOneSnapshot = childOne as? DataSnapshot {
                storyIDKeyList.append(Int(childOneSnapshot.key)!)
            }
        }
        completion(true)
    }
}

Old answer (Works too):

func saveRetrieveStoryID(completion: @escaping (Bool) -> Void) {

    let userID = Auth.auth().currentUser?.uid

    let storyIDRef = DBRef.child("Story IDs").child(userID!)
    storyIDRef.observe(.value) { (snapshot) in

        for childOne in snapshot.children {

            if let childOneSnapshot = childOne as? DataSnapshot {
                storyIDKeyList.append(Int(childOneSnapshot.key)!)
            }
        }
        storyIDRef.removeAllObservers()
        completion(true)
    }
}