title: View-based NSTableView in Swift does not show content
body: <p>I'm trying to show a very basic data structure in a view-based NSTableView. After hours of searching, I finally got to a point where most of the table is set up. The number of rows is correct, I know the <code>func tableView(tableView: NSTableView, objectValueForTableColumn tableColumn: NSTableColumn?, row: Int)</code> method is executed for all cells because it prints the correct data in the console. Unfortunately, the table shows with the default value instead of the <code>String</code>s from my data array.</p>
  
  <p><a href="https://i.stack.imgur.com/F9Vx4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/F9Vx4.png" alt="The table view doesn&#39;t display the correct data"></a></p>
  
  <p>Here's the code:</p>
  
  <p>ViewController.swift</p>
  
  <pre><code>import Cocoa
  
  class ViewController: NSViewController {
  
      @IBOutlet weak var myTableView: NSTableView!
      var files = [FilesListData]()
  
      override func viewDidLoad() {
          super.viewDidLoad()
          self.setupSampleFiles()
      }
      override func viewDidAppear() {
          super.viewDidAppear()
      }
  
      func setupSampleFiles() {
          let file1 = FilesListData(file: "test.mp3", title: "test")
          let file2 = FilesListData(file: "test2.mp3", title: "test 2")
  
          self.files = [file1, file2]
      }
  }
  
  extension ViewController: NSTableViewDataSource {  
      func numberOfRowsInTableView(tableView: NSTableView) -&gt; Int {
          return self.files.count
      }
  
      func tableView(tableView: NSTableView, objectValueForTableColumn tableColumn: NSTableColumn?, row: Int) -&gt; AnyObject? {
          let cellView: NSTableCellView = tableView.makeViewWithIdentifier((tableColumn!.identifier), owner: self) as! NSTableCellView
  
          let fileData = self.files[row]
          if tableColumn!.identifier == "fileCol" {
              cellView.textField!.stringValue = fileData.file
          } else if tableColumn!.identifier == "titleCol" {
              cellView.textField!.stringValue = fileData.title
          } else {
              cellView.textField!.stringValue = "N/A"
          }
          return cellView
      }
  }
  
  extension ViewController: NSTableViewDelegate {
  }
  </code></pre>
  
  <p>FilesListData.swift</p>
  
  <pre><code>import Foundation
  
  class FilesListData: NSObject {
      var file: String
      var title: String
  
      override init() {
          self.file = String()
          self.title = String()
      }
  
      init(file: String, title: String) {
          self.file = file
          self.title = title
      }
  }
  </code></pre>
  
  <p>A few more notes: in the storyboard, I did create an outlet for <code>dataSource</code> and <code>delegate</code> to the View Controller. The identifiers of my first 2 columns are set to "fileCol" and "titleCol". The project compiles and runs without any error or warning. Below are a few screenshots of my storyboard.</p>
  
  <p><a href="https://i.stack.imgur.com/9QLdE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9QLdE.png" alt="Objects tree"></a></p>
  
  <p><a href="https://i.stack.imgur.com/0pLod.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0pLod.png" alt="Identifier for the first column"></a></p>