title: How to go back to previous view controller of different storyboard?
body: <p>I have 2 storyboards say A and B. Storyboard A has multiple view controllers. After some user action I switch from storyboard A to storyboard B. How can I go back to previous storyboard A on clicking back button and go back to same view controller  I  initially came from. </p>
  
  <p>I can't do as given below because I will not have the old navigation stack of A.</p>
  
  <pre><code> let storyboard =  UIStoryboard(name: "A", bundle: nil)
      let vc = storyboard.instantiateInitialViewController() as UIViewController!
      presentViewController(vc, animated: true, completion: nil)
  </code></pre>