title: what does `@objc(ViewController) ` do?
body: <p>I have this swift code:</p>
  
  <pre><code>func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject : AnyObject]?) -&gt; Bool {
  ...
      let storyboard = UIStoryboard(name: "Main", bundle: nil)
          let controller = storyboard.instantiateInitialViewController()!
          if (controller is InlineMainViewController ){
              mainViewController = controller as! InlineMainViewController
          }
          window?.rootViewController = controller
          window?.makeKeyAndVisible()
  }
  </code></pre>
  
  <p>when my viewController has this attribute:</p>
  
  <pre><code>@objc(ViewController)  // match the ObjC symbol name inside Storyboard
  public class InlineMainViewController: UIViewController, 
  </code></pre>
  
  <p><code>(controller is InlineMainViewController )</code> returns <code>false</code></p>
  
  <p>and when it doesn't have this attribute:</p>
  
  <pre><code>public class InlineMainViewController: UIViewController, 
  </code></pre>
  
  <p><code>(controller is InlineMainViewController )</code> returns <code>true</code></p>
  
  <p>My <code>Main.sotryboard</code> is connected to <code>InlineMainViewController</code></p>
  
  <p>I took <code>@objc(ViewController)</code> from Google analytics github example</p>