title: NSTableView Cell with Identifier keep giving nil
body: <p>I am working on building MacOS app. I am trying to make table view that updates the cell when I press add button. </p>
  
  <p><a href="https://i.stack.imgur.com/g0CF5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/g0CF5.png" alt="enter image description here"></a></p>
  
  <p>Following is my code:</p>
  
  <pre><code> func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -&gt; NSView? {
      let identifier = tableColumn?.identifier as NSString?
      if ( identifier == "NameCell")
      {
          var result: NSTableCellView
          let cell = tableView.make(withIdentifier: "NameCell", owner: self) as! NSTableCellView
          cell.textField?.stringValue = self.data[row].setting!
              return cell
  
      }
      else if (identifier == "SettingCell")
      {
          if let cell = tableView.make(withIdentifier: "SettingCell", owner: self) as? NSTableCellView {
          cell.textField?.stringValue = self.data[row].setting!
          return cell
      }
      }
      return nil
  }
  </code></pre>
  
  <p>However, the line             let cell = tableView.make(withIdentifier: "NameCell", owner: self) as! NSTableCellView is keep failing because it returns nil </p>
  
  <p>fatal error: unexpectedly found nil while unwrapping an Optional value</p>
  
  <p>NameCell is from 
  <a href="https://i.stack.imgur.com/EYr1i.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EYr1i.png" alt="enter image description here"></a>
  Can anyone please help me find a way to solve this problem? </p>