title: NSNumberFormatter to format US Telephone Numbers
body: <p>I'm trying to convert a string of numbers, entered by the user, into a sexy string like Phone.app on the iPhone. Here is the code I'm using, which doesn't work (no special format comes out) and after a certain number of digits it just starts adding "0" to the end of the string.</p>
  
  <pre><code>NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
  [formatter setNumberStyle:NSNumberFormatterNoStyle];
  [formatter setPositiveFormat:@"+# (###) ###-###"];
  [formatter setLenient:YES];
  NSString *strDigits = [self stringByReplacingOccurrencesOfRegex:@"[^0-9+]" withString:@""];
  return [formatter stringFromNumber:[NSNumber numberWithDouble:[strDigits doubleValue]]];
  </code></pre>