title: IBoutlet is nil in my custom table cell?
body: <p>//custom cell in one swift file <br></p>
  
  <pre><code>import UIKit
  
  class CardTableViewCell: UITableViewCell {
  
      @IBOutlet weak var elapsedTime: UILabel!
      @IBOutlet weak var todo: UILabel!
      @IBOutlet weak var startAndStop: UIView!
      @IBOutlet weak var progress: UIView!
      @IBOutlet weak var cardView: UIView!
  
  }
  </code></pre>
  
  <p>//custom Table view controller in another swift file</p>
  
  <pre><code>import UIKit
  
  class CardFeedTableViewController: UITableViewController {
  
      override func viewDidLoad() {
          super.viewDidLoad()
          tableView.register(CardTableViewCell.self, forCellReuseIdentifier: "cardCell")
          tableView.delegate = self
          tableView.dataSource = self
      }
  
      // MARK: - Table view data source
  
      override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -&gt; Int {
          // #warning Incomplete implementation, return the number of rows
          return 3
      }
  
  
      override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -&gt; UITableViewCell {
          let cell: CardTableViewCell = self.tableView.dequeueReusableCell(withIdentifier: "cardCell", for: indexPath) as! CardTableViewCell
          cell.todo.text = "study"
          return cell
      }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/ChfD9.png" rel="nofollow noreferrer">running the app triggers a error</a></p>
  
  <p><a href="https://i.stack.imgur.com/ShxZJ.png" rel="nofollow noreferrer">storyboard</a></p>
  
  <p>I don't know why all the properties in the my table cell is nil, when I run the app.</p>