title: What is the extend edge property in UIViewController for ?
body: <p>I have read on the forums about this property, mostly its people setting this this property to false or unchecking it in the storyboard. 
  I have done this myself because when I have a UINavigation Controller embedded in a View, the top bar pushes my UITextView down so the text starts editing at the bottom. </p>
  
  <p>Unchecking Extended Edges Under Top Bars in the StoryBoard in the UIViewController solves my problem but I don't understand what is going on. </p>
  
  <p>Can someone give an explanation on what the purpose of this property is, I would like to know more about it. </p>