title: NSArray and NIL values. How to return the number ("count") of non-NIL values the array
body: <p>I have two questions regarding an NSArray:</p>
  
  <ul>
  <li>How can I add nil values to the array? Would be adding <code>[NSNull
  null]</code> be correct? </li>
  <li>What would be the best code to
  return the number (count) of nil and non-nil values of this array in
  your view?</li>
  </ul>
  
  <p>Thank you!!</p>