title: Swift 3: stringByReplacingCharactersInRange alternatives
body: <p>Any of you knows an <code>stringByReplacingCharactersInRange</code> to be use in Swift 3?</p>
  
  <p>I'm trying to convert this <code>Objective-C</code> to <code>Swift</code>:</p>
  
  <pre><code>strToSort = [strToSort stringByReplacingCharactersInRange:NSMakeRange((i-1),1) withString: [strToSort substringWithRange:NSMakeRange((i),1)]];
  </code></pre>
  
  <p>I'll really appreciate your help.</p>