Table View not populating data, but my print statements are working - swift4

Question

When I run the below code, I am getting the proper JSON version and list of bonus codes in my console log, but the table view itself is not showing any data.
import UIKit
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet weak var tableView: UITableView!
var bonuses = [JsonFile.JsonBonuses]()
override func viewDidLoad() {
super.viewDidLoad()
downloadJSON {
self.tableView.reloadData()
}
tableView.delegate = self
tableView.dataSource = self
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
print("Found \(bonuses.count) rows in section.")
return bonuses.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = UITableViewCell(style: .default, reuseIdentifier: nil)
cell.textLabel?.text = bonuses[indexPath.row].name.capitalized
return cell
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
performSegue(withIdentifier: "showDetails", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? HeroViewController {
destination.bonus = bonuses[(tableView.indexPathForSelectedRow?.row)!]
}
}
// MARK: - Download JSON from ToH webserver
func downloadJSON(completed: #escaping () -> ()) {
let url = URL(string: "http://tourofhonor.com/BonusData.json")
URLSession.shared.dataTask(with: url!) { [weak self] (data, response, error) in
if error == nil {
do {
let posts = try JSONDecoder().decode(JsonFile.self, from: data!)
DispatchQueue.main.async {
completed()
}
print("JSON Version \(posts.meta.version) loaded.")
print(posts.bonuses.map {$0.bonusCode})
self?.bonuses = posts.bonuses
} catch {
print("JSON Download Failed")
}
}
}.resume()
}
}
The code is based off a tutorial I found online that originally used DOTA character information to populate the data. I changed it to using my own JSON feed, which seems to be valid since I can see the bonus codes in the console, but isn't putting any data on display in the app.

Answer 1

The API is working Asynchronously, hence table is loaded before the API call finishes. So you have to reload the table after API fetches the results.
print(posts.bonuses.map {$0.bonusCode})
self?.bonuses = posts.bonuses
DispatchQueue.main.async {
//reload table in the main queue
self.myTableView.reloadData()
}
}

Answer 2

The issue is that you are calling the completion closure before filling the self.bonuses array, try putting it after that line.
I will also recommend putting these lines:
tableView.delegate = self
tableView.dataSource = self
Before calling the downloadJSON method.