title: Reversing a string in Swift 4.2
body: <p>iOS 11, Swift 4.2, Xcode 10</p>
  
  <p>Looking at SO and indeed googling all seem to suggest this should work, but it doesn't.</p>
  
  <pre><code>let str = self.label!.text
  let newStr = String(str?.reversed())
  </code></pre>
  
  <p>I get an error message Cannot invoke initializer for type 'String' with an argument list of type '(ReversedCollection?)... so how do I get my string back?</p>