title: Is there an easy method to check is an NSRange passed to substringWithRange on NSString exists (so not to cause an error)?
body: <p>Say I pass the NSRange of (location: 5, length: 50) on the NSString "foo", that range obviously doesn't exist. </p>
  
  <p>Is there a way to say <code>[string rangeExists:NSRange]</code> for instance, or do we have to manually validate the input?</p>