Save Firebase structure in UITableView Array [Swift 4]

Question

I am new to programming and currently trying to make a newsfeed like app. My goal is it to notice changes in the firebase database through my app and new posts in my table view. Currently I am able to show one post in my tableView. Its only changing though when you reopen the ViewController. One of my problem is that I don't know how to use any other command then obserSingleEvent and I am pretty sure that one of my main mistakes. So my questions are: 1. How do I make the tableView instantly reload when a change appears? 2. how do I display more then one post? (3. how can I show the most recent posts first?)

class ViewController: BaseViewController, UITableViewDelegate, UITableViewDataSource {

@IBOutlet var newsfeedTableView: UITableView!

var ref: DatabaseReference!

var posts = [String]()

override func viewDidLoad() {
    super.viewDidLoad()
    addSlideMenuButton()

    ref = Database.database().reference()

    ref.child("posts").queryOrderedByKey().observeSingleEvent(of: .childAdded, with: { snapshot in

        let newPost = snapshot.value as? String
        self.posts.append(newPost!)
        print("newPost: \(newPost)")
        print("posts: \(self.posts)")
        self.newsfeedTableView.reloadData()
        print("reloadData")
    })

}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return (posts.count)
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = UITableViewCell(style: UITableViewCell.CellStyle.default, reuseIdentifier: "cell")

    cell.textLabel?.text = posts[indexPath.row]
    print("posts in cell: \(posts)")

    return cell
}
}

Rawand Ahmed Shaswar · Accepted Answer · 2018-12-05 12:07:56Z

1

You're observing with singleEvent which is wrong for the intended use.

ref.child("posts").observe( .childAdded, with: { snapshot in

    let newPost = snapshot.value as? NSDictionary
    let post_title:String = newPost!["post_title"] as? String ?? "error"
    self.posts.append(post_title)

    print("newPost: \(newPost)")
    print("posts: \(self.posts)")
    self.newsfeedTableView.reloadData()
    print("reloadData")
})

Also, that sorting system won't work for a news app. you can't work with human-provided 1,2,3. could you update it to something like this from now on:

(1 - 2) A random-unique generated post ID

PS. It's impossible for Firebase to order your post list with post, post1, post2. So in this case queryOrderedByKey() is useless.

Making the posts 1,2,3 would work for the ordering system

answered Dec 5, 2018 at 12:07

Rawand Ahmed Shaswar

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3 Comments

Roman H Over a year ago

Works! Wow great. Thank you, mate.

Rawand Ahmed Shaswar Over a year ago

I'm sure you'll build great apps with Firebase, Keep up the good work

Jay Over a year ago

@RomanH Ordering by key is fine but you may find it's a bit limiting. Creating your keys with .childByAutoId is spot on but your may want to consider adding a child node within each node called index which is an Int. Store the integer order within each index and it will give you more flexibility. You can even store reverse_index as negative numbers for reverse ordering.

Galo Torres Sevilla · Accepted Answer · 2018-12-05 12:14:09Z

1) You can implement a function that is constantly observing the data in Firebase for changes and update the array. But be careful with that, it will be consuming memory and also you will get a lot of network usage.

.observe // instead of .observeSingleEvent will do that

Again, it would be better if you add a refresher to the tableView so you fetch the data on demand instead of all the time.

2) Your array is fine. I'll move the call to firebase to another function instead of having it in viewDidLoad().

3) You need to store a timeStamp in firebase to get this functionality. Yes, you can queryOrdered but remember firebase is async. Data will be given as available so it would be better to sort the array depending on the creation timeStamp of each of the items.

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