title: Passing data with unwind segue
body: <p>I created two view controllers. I created a segue from the first to the second to pass data. Now I want to pass data from the second view controller to the first one. I went through many similar questions and I'm not able to implement those as I lack the knowledge on how unwinding works. </p>
  
  <p><strong>ViewController.swift</strong></p>
  
  <pre><code>class ViewController: UIViewController
  {   
      var dataRecieved: String?
      @IBOutlet weak var labelOne: UILabel!
      @IBAction func buttonOne(sender: UIButton)
      {
          performSegueWithIdentifier("viewNext", sender: self)
      }
      override func prepareForSegue(segue: (UIStoryboardSegue!), sender: AnyObject!)
      {
  
          var svc: viewControllerB = segue.destinationViewController as! viewControllerB
          svc.dataPassed = labelOne.text
      }
  }
  </code></pre>
  
  <p>This will pass the data to dataPassed in view controller "viewControllerB". Say, now I want to pass some data from viewControllerB to dataRecieved in ViewController. How can I do this with only unwind segue and not by using delegate. I'm quite new to swift, would appreciate a detailed explanation.</p>