title: Global constants file in Swift
body: <p>In my Objective-C projects I often use a global constants file to store things like notification names and keys for <code>NSUserDefaults</code>. It looks something like this:</p>
  
  <pre><code>@interface GlobalConstants : NSObject
  
  extern NSString *someNotification;
  
  @end
  
  @implementation GlobalConstants
  
  NSString *someNotification = @"aaaaNotification";
  
  @end
  </code></pre>
  
  <p>How do I do exactly the same thing in Swift?</p>