title: How to operate with character and the next character in objective-c
body: <p>I have a string with name, say, "John Doe", or "JohnDoe" and I want to get "John-Doe" as a result.
  I can't replace " " with "-" because sometimes there's no " ". So I thought of this:</p>
  
  <p>if letter is in lowercase and the next is uppercase, then input "-".</p>
  
  <p>How would i do that?</p>