title: Resolution failed exception in Xamarin IOS prism
body: <p>I have an iOS application written in Xamarin and I am getting a Unity Exceptions Resolution Failed exception when I try and run the application in iOS. However this error does not happen when I run the android version of the application. The exception is being thrown while the initalize function from prism is taking place.</p>
  
  <p>Here is a snippet from my app.xaml.cs</p>
  
  <pre><code>protected override void RegisterTypes(IContainerRegistry containerRegistry)
      {
          this.RegisterLocal(containerRegistry);
          this.RegisterServices(containerRegistry);  
          this.RegisterPagesForNavigation(containerRegistry);
      }
  </code></pre>
  
  <p>This code all executes and passes.</p>
  
  <p>This is the iOS initialization</p>
  
  <pre><code>Register("AppDelegate")]
  public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
  {
      public override bool FinishedLaunching(UIApplication app, NSDictionary options)
      {
  
          global::Xamarin.Forms.Forms.Init();
  
          PullToRefreshLayoutRenderer.Init();
  
          LoadApplication(new App(new IosInitializer()));
  
          return base.FinishedLaunching(app, options);
      }
  
      public class IosInitializer : IPlatformInitializer
      {
          public void RegisterTypes(IContainerRegistry containerRegistry)
          {
              containerRegistry.Register&lt;IUAirshipUpdate, UAirshipUpdate&gt;();
          }
      }
  </code></pre>
  
  <p>This code also executes</p>
  
  <p>The exception being thrown is an argument null exception indicating that IModuleCatelog is not present. I do not understand why it is looking for that module and can not find it. The source code on GitHub indicates that class was registered.</p>