title: iAds not displayed on app's first screen - ad not loaded
body: <p>I am following <a href="https://developer.apple.com/library/ios/technotes/tn2264/_index.html#//apple_ref/doc/uid/DTS40011827-CH1-SHARE_ADBANNERVIEW_INSTANCES_ACROSS_VIEWS" rel="nofollow">Apple's best practices for iAd</a> in creating a single iAd banner ad object for the whole app in my app delegate - as it says, you should create a single <code>ADBannerView</code> and share it across all views. I call the following method to initialize it in my app delegate:</p>
  
  <pre><code>- (void)initializeAds {
       // bannerAd is a property of MyAppDelegate
       bannerAd = [[ADBannerView alloc] initWithFrame:CGRectZero];
       bannerAd.delegate = self;
       bannerAd.currentContentSizeIdentifier = ADBannerContentSizeIdentifierPortrait;
  }
  </code></pre>
  
  <p>And then in my UIViewController, I refer to</p>
  
  <pre><code>MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
  ADBannerView *myBannerView = appDelegate.bannerAd;
  </code></pre>
  
  <p>This works great in most of my app, running my ad display code for the current UIViewController in <code>viewDidAppear:</code>. However, on the first UIViewController (the root UIViewController), when the app is initially opened it does not display an ad. It seems that it hasn't yet loaded an ad. But when I navigate down to another UIViewController, and then go back, the ad is displayed, presumably because it had a chance to load an ad. I am running my test device with a 100% fill rate. How can I force iAd to try to get an ad before my code is run?</p>