CollectionView duplicating data after a new post - ios

Question

I cannot seem to figure out why my data keeps duplicating after a new post has been made. When the app starts everything looks as it should and the data is presented properly from firebase.
After I make a new post and return to my feed the new data appears but the old data has been duplicated.
Here is my code,
override func viewDidAppear(_ animated: Bool) {
ref = FIRDatabase.database().reference()
ref.child("brackets").observe(FIRDataEventType.value, with: { (snapshot) in
if let bracketsSnapshot = snapshot.children.allObjects as? [FIRDataSnapshot] {
for brackets in bracketsSnapshot {
if let bracketsDict = brackets.value as? Dictionary <String, Any> {
let key = brackets.key
let post = BracketsPublicFeed(postKey: key, postData: bracketsDict)
self.posts.append(post)
}
}
}
self.collectionView.reloadData()
})
}
Here is the code used when posted,
func PostData(itemToCell1: String, itemToCell2: String, itemToCell3: String, itemToCell4: String, userName: String?/*, userID: String?*/) {
let ref : FIRDatabaseReference!
ref = FIRDatabase.database().reference()
let votes = 0
let userName = ""
let key = ref.child("brackets").childByAutoId().key
let post = [
"userID": userID as AnyObject,
"item1": itemToCell1 as AnyObject,
"item2": itemToCell2 as AnyObject,
"item3": itemToCell3 as AnyObject,
"item4": itemToCell4 as AnyObject,
"userName": userName as AnyObject,
"votes": votes as AnyObject ]
let childUpdates = ["/brackets/\(key)": post,
"/user-posts/\(userID)/\(key)/": post]
ref.updateChildValues(childUpdates)
}
I have tried various things such as,
ref.removeAllObservers()
self.posts.removeAll()
in the viewDidDisappear
I will gladly post more code if I am not painting the whole picture.
UPDATE,
Thanks for your responses guys. So far none of them have worked except for the suggestion to use ref.child("brackets").removeAllObservers()
The thing is though it that it works exactly as it should when I write this code,
self.posts.removeAll()
ref.child("brackets").removeAllObservers()
So I get rid of everything and reload it every time the view appears.

Answer 1

From Firebase docs:
- (void) removeAllObservers
Removes all observers at the current reference, but does not remove any observers at child references.
removeAllObservers must be called again for each child reference where a listener was established to remove the observers.
So, ref.removeAllObservers() in viewDidDisappear won't remove observer for ref.child("brackets").
Try this in viewDidDisappear:
ref.child("brackets").removeAllObservers()

Answer 2

did you try observerSingleEvent? Seems like you're keep adding new observer every time view appears. There is, actually, neat way to use FirebaseCollectionViewDataSource without populating data manually, like this:
dataSource = FirebaseCollectionViewDataSource.init(query: ref.child("brackets"),
modelClass: Post.self,
nibNamed: "PostViewCell",
cellReuseIdentifier: "lesson",
view: self.collectionView)

Answer 3

You're listening for a .Value event, which triggers with the entire list each time that the data changes (such as when an item is added). So the first time it triggers with e.g. items 1, 2 and 3. Then next time it triggers with items 1, 2, 3 and 4.
You can deal with this in two ways:
clear the collection view every time
respond to .ChildXxx events instead
The first is simplest, but will lead to a flickering UI. So I'll show the second option: responding to .ChildAdded.
A .ChildAdded event is fired for every existing child when you first attach the observer. So that's items 1, 2 and 3. When you then add a new item, it will fire with only item 4. That allows you to simply add the new item to the collection view:
ref.child("brackets").observe(FIRDataEventType.ChildAdded, with: { (snapshot) in
if let bracketsDict = snapshot.value as? Dictionary <String, Any> {
let key = brackets.key
let post = BracketsPublicFeed(postKey: key, postData: bracketsDict)
self.posts.append(post)
self.collectionView.reloadData()
})
Note: I didn't compile this code, so you may have to fix some problem with it. If you do, leave comments and I'll update.