title: Check string for nil & empty
body: <p>Is there a way to check strings for <code>nil</code> and <code>""</code> in Swift? In Rails, I can use <code>blank()</code> to check. </p>
  
  <p>I currently have this, but it seems overkill:</p>
  
  <pre><code>    if stringA? != nil {
          if !stringA!.isEmpty {
              ...blah blah
          }
      }
  </code></pre>