title: change label from another viewcontroller on swift
body: <p>I want to change label from another <code>viewController</code>.</p>
  
  <p>First viewcontroller is <code>MenuController</code>. Second one is <code>LoginViewController</code>.</p>
  
  <p>I want to change MenuController's <code>Label.text</code> from <code>LoginViewController</code>.</p>
  
  <p>In <code>LoginViewController</code>:</p>
  
  <pre><code>let viewController = MenuController()
  viewController.changeLabel("logout")
  </code></pre>
  
  <p>In <code>MenuController</code>:</p>
  
  <pre><code>class MenuController: UITableViewController {
      var attractionImages = [String]()
      var attractionNames = [String]()
      var webAddresses = [String]()
  
      @IBOutlet weak var loginLabel: UILabel!
  
  
      override func viewDidLoad() {
          super.viewDidLoad()
  
          loginLabel.text = "Login"
          print(loginLabel.text)
  
      }
  
      func changeLabel(Log: String)O {
          self.loginLabel.text = log
          print (log)
      }
  </code></pre>
  
  <p>But an error occur.</p>
  
  <blockquote>
    <p>fatal error: unexpectedly found nil while unwrapping an Optional value</p>
  </blockquote>
  
  <p>How can I solve it?</p>
  
  <p>Thanks for your help.</p>