title: What is the replacement for isDigit() for characters in Swift?
body: <p>As mentioned in <a href="https://stackoverflow.com/questions/24502669/swift-how-to-find-out-if-letter-is-alphanumeric-or-digit">this post</a>, before Xcode 6 Beta 4, one could use <code>c.isDigit()</code> and <code>c.isAlpha()</code> to find if <code>c : Character</code> was a digit or alpha. The post mentions that this was removed as it was only effective for ASCII characters. </p>
  
  <p>My question is, what's the replacement? Short of setting up a function with a switch statement for alphanumeric options, how can I test a character on its digit-ness?</p>