Swift showing Firebase duplicating data (.observeChildAdded) not working - swift

Question

Each time I add a new post to the database, the amount of times the posts show is increased by one. For instance, when I add one new post, the number of times the posts are duplicated is once. When I add another post (the view is reloaded) I see all the posts three times. I assume that the problem is with the function fetchPosts(), as each time the view loads it collects all the data from the firebase and appends it to the array. I have already tried emptying the array in the view did load, but that only makes all the posts show even more times. Also, I have tried using observe(.childAdded) and that results in no posts showing at all.
var ref: DatabaseReference!
var postList = [Post]()
var refHandle : UInt!
#IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
checkForSignedIn ()
ref = Database.database().reference().child("posts")
fetchPosts()
}
public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return postList.count
}
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! PostTableViewCell
//set cell content
let contentOfCellPost = postList[indexPath.row]
cell.label?.text = contentOfCellPost.post_words
cell.revealCount.text = contentOfCellPost.Reveals
return cell
}
public func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
let tableSize = tableView.bounds.height
return tableSize
}
func fetchPosts () {
let query = ref.queryOrdered(byChild: "timestamp").queryLimited(toFirst: 10)
query.observe(.value) { (snapshot) in
for child in snapshot.children.allObjects as! [DataSnapshot] {
if let value = child.value as? NSDictionary {
let post = Post()
let poster = value["poster"] as? String ?? "Name not found"
let post_content = value["post"] as? String ?? "Content not found"
let post_reveals = value["Reveals"] as? String ?? "Reveals not found"
post.post_words = post_content
post.poster = poster
post.Reveals = post_reveals
post.postID = child.key
self.postList.append(post)
print (post.post_words ?? "none")
DispatchQueue.main.async { self.tableView.reloadData() }
//make this for when child is added but so that it also shows psots already there something like query.observre event type of
}
}
}
}
The console log at first, for instance, will show the correct number of posts :
Thrice
Twice
Once
Tttt
Bloop
Decimal
9
7
3
When I add a new post, it shows this:
Tattoo
Thrice
Twice
Once
Tttt
Bloop
Decimal
9
7
3
Tattoo
Thrice
Twice
Once
Tttt
Bloop
Decimal
9
7
3
Tattoo
Thrice
Twice
Once
Tttt
Bloop
Decimal
9
7
3
Tattoo
Thrice
Twice
Once
Tttt
Bloop
Decimal
9
7
3

Answer 1

You need to clear your model (self.postList) at the beginning of the .observe block like so:
query.observe(.value) { (snapshot) in
self.postList.removeAll() //or however you can clear it
for child in snapshot.children.allObjects as! [DataSnapshot] {
if let value = child.value as? NSDictionary {
let post = Post()
let poster = value["poster"] as? String ?? "Name not found"
let post_content = value["post"] as? String ?? "Content not found"
let post_reveals = value["Reveals"] as? String ?? "Reveals not found"
post.post_words = post_content
post.poster = poster
post.Reveals = post_reveals
post.postID = child.key
self.postList.append(post)
print (post.post_words ?? "none")
DispatchQueue.main.async { self.tableView.reloadData() }
//make this for when child is added but so that it also shows psots already there something like query.observre event type of
}
}
Currently, each time the database is updated with a post, you add all posts to your model once again. Therefore you must clear your model each time you fetch all posts.
The reason why this doesn't work in viewDidLoad is because viewDidLoad is called only once, in the beginning, and not everytime the view appears -- thus the data will not be cleared upon adding a post.
Alternatively, you can use .childAdded -- but then you need to change the way you parse it because each snapshot with .childAdded returns a single post, not all the posts together.