title: Swift 3: Passing Data Forward Doesn't Work/Crashes
body: <p>Hi so I'm pretty new to swift and I am trying a simple task: pass data between view controllers. I know that this is pretty easy in SWIFT 2 but I can only find a few articles for this using Swift 3. </p>
  
  <p>Here is my simplified code: </p>
  
  <pre><code>class logInView: UIViewController {
  
      @IBOutlet weak var l1: UILabel!
      @IBOutlet weak var l2: UILabel!
      @IBOutlet weak var username: UITextField!
      @IBOutlet weak var password: UITextField!
  
      @IBAction func submit(_ sender: UIButton) {
          // Get User Input
          let user = username.text
          let pass = password.text
          print(user)
          print(pass)
      }
  
      override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
          if segue.identifier == "logInToInfoSegue"{
              if let destination = segue.destination as? infoView {
                  // stuff inside 
  
              }
          }
      }
  
  }
  </code></pre>
  
  <p>The segue name from the first view to the second is named <code>logInToInfoSegue</code>.
  The first view controller is named <code>logInView</code>.
  The second view controller is named <code>infoView</code>.
  So my questions are: </p>
  
  <ol>
  <li><p>What code do I need to pass the data from the entered text to the next view controller, because the link above doesn't work for me. </p></li>
  <li><p>Why is <code>if segue.identifier == "logInToInfoSegue"</code> line of code giving me a Thread 1 SIGABRT error and crashing my app?</p></li>
  </ol>
  
  <p>Please explain the code if you can answer, I'm still really new to swift but I have moderate experience with other languages.</p>