title: Changing object type to instance of child class in Swift
body: <p>Array contains shapes and named shapes objects. Shape is a parent for named shape and only difference is name property.</p>
  
  <p>When user want to give name to shape. Object of type shape suppose to be converted to type named shape.</p>
  
  <p>How do I do it using swift and is it proper thing to do?</p>