title: How to define category bit mask enumeration for SpriteKit in Swift?
body: <p>To define a category bit mask enum in Objective-C I used to type:</p>
  
  <pre><code>typedef NS_OPTIONS(NSUInteger, CollisionCategory)
  {
      CollisionCategoryPlayerSpaceship = 0,
      CollisionCategoryEnemySpaceship = 1 &lt;&lt; 0,
      CollisionCategoryChickenSpaceship = 1 &lt;&lt; 1,
  };
  </code></pre>
  
  <p>How can I achieve the same using <code>Swift</code>? I experimented with enums but can't get it working. Here is what I tried so far.</p>
  
  <p><img src="https://i.stack.imgur.com/6cMHI.png" alt="error screenshot"></p>