title: Swift : How to change navigation controller's height without adding a toolbar
body: <p>How to change navigation controller's height without adding a toolbar ?
  Here is an example of apple's iBooks app that I want to build.
  I've a solution but isn't perfect( adding a toolbar below the nav controller but it is very ugly)</p>
  
  <p><img src="https://i.stack.imgur.com/p1705.jpg" alt="ibook Nav Controller is perfect "></p>
  
  <p><img src="https://i.stack.imgur.com/JiMjy.png" alt="I added a toolbar below the nav controller "></p>