XCode Swift 3 UITableViewController Cell doesn't show - ios

Question

I am exporting json file from itunes api>converted that to a json file>send that to firebase> brought that in to a dictionary file here and now I am trying to put that into a tableview but it does not seem to work and I have no clue why. I checked that:
1. The file that I imported was successfully converted into a dictionary.
2. Datasource and delegate is connected to this UITableViewController file.
3. Put other arrays to check if my connections were right(and it worked but it does not work at all if I use the data that I brought in with Firebase)
4. I put cell style as subtitle and type as dynamic.
Below is the UITableViewController code:
import UIKit
import Firebase
class TableViewController1: UITableViewController {
var ref: FIRDatabaseReference!
var rank = [String]()
var song = [[String]]()
var artist = [[String]]()
var tna = [String]()
override func viewDidLoad() {
super.viewDidLoad()
self.ref = FIRDatabase.database().reference()
let userID = FIRAuth.auth()?.currentUser?.uid
self.ref.child("top100itunes").observeSingleEvent(of: .value, with: { (snapshot) in
let jsonfile = snapshot.value! as! String
//print(jsonfile)
let jsondict:[String:Any] = self.convertToDictionary(text: jsonfile)!
for (key, value) in jsondict {
if key != nil {
self.rank.append(key)
if value != nil{
self.tna.append(value as! String)
}
}
}
for x in self.tna{
if x != nil {
for (key,value) in self.convertToDictionary(text: x)!{
self.song.append([key])
self.artist.append([value as! String])
}
}
}
}, withCancel: nil)
}
// Uncomment the following line to preserve selection between presentations
// self.clearsSelectionOnViewWillAppear = false
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem()
func convertToDictionary(text: String) -> [String: Any]? {
if let data = text.data(using: .utf8) {
do {
return try JSONSerialization.jsonObject(with: data, options: []) as? [String: Any]
} catch {
print(error.localizedDescription)
}
}
return nil
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return self.song.count
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
return self.song[section].count
}
override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return self.rank[section]
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell2", for: indexPath)
cell.textLabel?.text = self.song[indexPath.section][indexPath.row]
cell.detailTextLabel?.text = self.artist[indexPath.section][indexPath.row]
return cell
}
}
The json file that I imported is in the structure like:
{ 1 : { Title : Artist },
2 : { Title : Artist },
.....
}

Answer 1

observeSingleEvent() is asynchronous and numberOfRowsInSection() will be getting called before observeSingleEvent() has finished populating the data.
If you put a call to self.tableView.reloadData() after the 2nd for loop then this will cause a refresh of the table view once the data has been populated.
Alternatively you could consider re-architecting your app so it has a separate model component that is responsible for data retrieval so that the data could have been populated before the view is launched if applicable.

Answer 2

Your code is doing this:
viewDidLoad
start firebase async
ask for tableview number of sections/rows
song.count is 0
tableview loads with no cells
firebase async completes and populates song array
... nothing else
After this method you should add tableView reloadData like so:
for x in self.tna{
if x != nil {
for (key,value) in self.convertToDictionary(text: x)!{
self.song.append([key])
self.artist.append([value as! String])
}
}
}
self.tableView.reloadData()
I agree with Halfman that you should rearchitect your application to separate out the model from the controller. Read up on MVC.
I also suggest that instead of maintaining multiple arrays (i.e. song, artist, tna) you use a single struct to manage all this data. Read up on Swift structures.
TableViewController1 isn't an optimal choice for a controller name. Maybe SongListTableViewController is more clear?