title: How can I enable iAd when using Sprite Kit?
body: <p>In IOS 7, we can enable iAd very easy when using:</p>
  
  <blockquote>
    <p>self.canDisplayBannerAds = YES;</p>
  </blockquote>
  
  <p>in code <strong>ViewDidLoad</strong> of UIViewController</p>
  
  <p>However, I cannot use this in my ViewController (the ViewControl that load SKScene). My game is crash when loading.</p>
  
  <p>So how can I active iAd in my game (using Sprite Kit)?</p>