title: How to call from a Popover a method of the main view controller?
body: <p>In a iOS project, I have a main ViewController and a second ViewController, the second ViewController is displayed as a Popover with a segue from a button in the navigationbar. In that popover there is a button with this code:</p>
  
  <pre><code>class Pop: UIViewController {
  
    @IBAction func colorOnePressed(_ sender: Any) {
          let vc = ViewController()
          vc. zoomIn()
      }
  
  }
  </code></pre>
  
  <p>This is the method of the first view controller:</p>
  
  <pre><code>class ViewController: UIViewController {
  
      @IBOutlet weak var mainTextField: UITextView!
      ...
  
      func zoomIn() {
          mainTextField.font = UIFont(name: "Helvetica Neue", size: CGFloat(18.00))
      }
  }
  </code></pre>
  
  <p>Unfortunately (and obviously for many of you) I get a fatal error: "unexpectedly found nil while unwrapping an Optional value".</p>