title: How to target iOS devices lower than a specific OS using @available
body: <p>I have a function that is aimed at iOS 11+ marked with the following:</p>
  
  <pre><code>@available(iOS 11.0, *)
  </code></pre>
  
  <p>Now I need to target a different function for iOS versions less than iOS 11. How do I write that?</p>