Ytukyg

I’m trying to modify code written a by a previous programmer. He wrote a getPostFromFirebase() function where it updates the tableview when 1) the app loads up due to it’s presence in viewDidLoad and 2) when there is a new post add by a user. The problem is that he used a .observe(.childAdded) event type which means when a post is deleted or modified, the tableView will not update(my end goal to do). When I change .childAdded to .value, the current data doesn’t get loaded upon launch. I’ve been banging my head against the wall to figure out a if let statement to add a .value event type so the view can refresh after any change(if that’s even possible). I’m familiar with Firebase RT DB hence how I was able to ID the observer issue but I’m no where near close to as good as I’d like to be so any help is appreciated.

func getPostFromFirebase() {

    let mostRecent = dbRef.lastestPostsQuery(count: 10)

    mostRecent.keepSynced(true)

    mostRecent.observe(.childAdded) { (snapshot: DataSnapshot) in



      /*parse method in the PostFetcher class 

      that returns the post data or an error by way of a tuple.*/



      let (post, error) = PostFetcher.parsePostSnapshot(snapshot: snapshot)  

      if let post = post {

        self.latestPosts.append(post)

        if let postId = post.postId { print("PostId = (postId)") }

      }

      if let error = error {

        print("(#function) - (error)")

      }

    }

  }

Edit:
Thanks to Franks help I was able to implement his suggestion and added a .removeAll() to remove the current state and have the view append a fresh snapshot. Whether a post is added or deleted, the view now updates as I'd like it to do.

func getPostFromFirebase() {

    let mostRecent = dbRef.lastestPostsQuery(count: 10)

    mostRecent.keepSynced(true)

    mostRecent.observe(.value) { (snapshot: DataSnapshot) in

        self.latestPosts.removeAll()

        for child in snapshot.children.allObjects as! [DataSnapshot] {

            let (post, error) = PostFetcher.parsePostSnapshot(snapshot: child)

            if let post = post {

                self.latestPosts.append(post)

                self.tableView.reloadData()

                if let postId = post.postId { print("PostId = (postId)") }

            }

            if let error = error {

                print("(#function) - (error)")

            }

        }

    }

}

The .child* events fire on child nodes of the location/query that you observe, while .value fires on the location/query itself. This means that the value you get is one level higher up in the JSON, and you'll need to loop over the results:

mostRecent.observe(.value) { (snapshot: DataSnapshot) in

  for child in snapshot.children.allObjects as! [DataSnapshot] {

    let (post, error) = PostFetcher.parsePostSnapshot(snapshot: child)  

    if let post = post {

      self.latestPosts.append(post)

      if let postId = post.postId { print("PostId = (postId)") }

    }

    if let error = error {

      print("(#function) - (error)")

    }

  }

}

Alternatively, you can listen to the .childChanged and .childRemoved events (in addition to .childAdded that you already have) and handle them separately. This may be better in cases where you need to update the UI efficiently, since it allows you to handle each individual case (new node, changed, node, removed node) in the most efficient way.