title: change to another screen after login is successful
body: <p>The use case of the app I am developing is I will have login view at the initial. When user logs in with valid credentials, the user should see another view saying welcome user. I am totally beginner and I don't know much more about xcode. I see the screen navigation from storyboard but I have already done many things in xib. </p>
  
  <p>Here is what I have done </p>
  
  <p><strong>SafariExtensionViewController.swift</strong></p>
  
  <pre><code>import SafariServices
  
  class SafariExtensionViewController: SFSafariExtensionViewController {
  
  
      @IBOutlet weak var passwordMessage: NSTextField!
      @IBOutlet weak var emailMessage: NSTextField!
      @IBOutlet weak var message: NSTextField!
      @IBOutlet weak var email: NSTextField!
      @IBOutlet weak var password: NSSecureTextField!
      static let shared = SafariExtensionViewController()
      override func viewDidLoad() {
          self.preferredContentSize = NSSize(width: 300, height: 250)
          message.stringValue = ""
          emailMessage.stringValue = ""
          passwordMessage.stringValue = ""
      }
  
  
      @IBAction func userLogin(_ sender: Any) {
          let providedEmailAddress = email.stringValue
          let providedPassword = password.stringValue
          let isEmailAddressValid = isValidEmailAddress(emailAddressString: providedEmailAddress)
          self.message.stringValue = ""
          emailMessage.stringValue = ""
          passwordMessage.stringValue = ""
          if isEmailAddressValid &amp;&amp; providedPassword.count &gt; 0 {
              // api call is done here
              // when success should show another screen
          } else {
              emailMessage.textColor = NSColor.red
              emailMessage.stringValue = "Invalid Email"
          }
      }    
  }
  </code></pre>
  
  <p>here is the screenshot of xib. </p>
  
  <p><a href="https://i.stack.imgur.com/OmiNy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/OmiNy.png" alt="enter image description here"></a></p>
  
  <p>Technology used</p>
  
  <p>swift 4</p>
  
  <p>xcode 9</p>
  
  <p>not IOS its mainly for app extension</p>
  
  <p>UPDATE</p>
  
  <p>I am not using storyboard and also it's not IOS. I am using xib and from macos project I am trying to develop app extension which will be shown in browser as an extension. </p>