title: NSTableView Delegate methods won't get called
body: <p>I'm currently trying to parse the reddit headlines from a specific subreddit and display these in an NSTableView. The thing is, the <code>numberOfRows</code> function gets called and returns the correct integer but the <code>tableView</code> delegate function never gets called. </p>
  
  <p>As far as I can see everything is wired up correctly in the code.</p>
  
  <p>ViewController:</p>
  
  <pre><code>@IBOutlet weak var tableView: NSTableView!
  
  override func viewDidLoad() {
      super.viewDidLoad()
      // Do any additional setup after loading the view.
      Downloader.load(url: URL(string: "https://www.reddit.com/r/" + "gaming" + ".json")!){
          (result) in
          let tvc = TableViewController(data: result)
  
          self.tableView.delegate = tvc
          self.tableView.dataSource = tvc
          self.tableView.reloadData()
      }
  }
  </code></pre>
  
  <p>TableViewController:</p>
  
  <pre><code>class TableViewController: NSObject{
  
      var json: JSON!
  
      init(data: JSON) {
          super.init()
          self.json = data
      }
  }
  extension TableViewController : NSTableViewDataSource {
      func numberOfRows(in tableView: NSTableView) -&gt; Int {
          return JSONFormatController.getTitlesFrom(json: json).count
      }
  }
  extension TableViewController : NSTableViewDelegate {
      func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -&gt; NSView? {
          var titles = JSONFormatController.getTitlesFrom(json: json)
          if let cell = tableView.make(withIdentifier: "entry", owner: nil) as? NSTableCellView {
              cell.textField?.stringValue = titles[row]
              return cell
          } else {
              return nil
          }
      }
  }
  </code></pre>
  
  <p>The <code>result</code> variable and <code>getTitlesFrom</code> method do work, I checked these.</p>