title: Swift 2 : Iterating and upper/lower case some characters
body: <p>I want to modify a Swift string by converting some characters to uppercase, some others to lowercase. </p>
  
  <p>In Obj-c I had following : </p>
  
  <pre><code>- (NSString*) lowercaseDestination:(NSString*) string {
      NSUInteger length = string.length;
      unichar buf[length+1];
      [string getCharacters:buf];
  
      BOOL up = true;
      for (int i=0; i&lt; length ; i++) {
          unichar chr = buf[i];
  
          if( .... ) {
              buf[i] = toupper(chr);
          } else {
              buf[i] = tolower(chr);
          }
      }
      string = [NSString stringWithCharacters:buf length:length];
      return string;
  </code></pre>
  
  <p>How would you do that in Swift 2 ? </p>
  
  <p>I did no find any <code>Character</code> method to upper or lower the case. </p>
  
  <p>Would be an array of <code>String</code> of 1 character be an option ? (And then use <code>String</code> methods to upper and lower each <code>String</code></p>