title: Determine viewWillAppear from Popped UINavigationController or UITabBarController
body: <p>I am unable to find a way to distinguish between popping from the Nav controller stack and entering the view controller from the UITabBarController.</p>
  
  <p>I want to call a method in ViewWillAppear only when the view is presented from the TabBar, not when someone presses back in the navigation controller.</p>
  
  <p>If I wasn't using a TabBarController, I could easily get this functionally using viewDidLoad.</p>
  
  <p>I've tried,</p>
  
  <pre><code>override func viewWillAppear(animated: Bool) {
      super.viewWillAppear(animated)
  
      println("View Will Appear")
  
      if isBeingPresented() {
          println("BP")
      }
      if isMovingFromParentViewController() {
          println("from")
      }
      if isMovingToParentViewController() {
          println("to")
      }
  }
  </code></pre>
  
  <p>But there is no difference when I present from pressing the Tab Button or when press back button.</p>
  
  <p>Only the "View Will Appear" is getting called.</p>
  
  <p>Using iOS 8.4 / Swift</p>