title: Cannot find type 'SKPaymentTransactionObserver' in scope
body: <p>I am trying to implement in-app purchases for my app.</p>
  <pre><code>import StoreKit
  import UIKit
  
  class BuyStoreViewController: UIViewController, SKProductsRequestDelegate, SKPaymentTransactionObserver {
  //code
  }
  </code></pre>
  <p>However, It keeps giving me the errors &quot;Cannot find type 'SKPaymentTransactionObserver' in scope&quot; and &quot;Cannot find type 'SKProductsRequestDelegate' in scope&quot;. I think it has something to do with the implementation of StoreKit, but I am not sure. Additionally, the &quot;SKProductsRequestDelegate&quot; and &quot;SKPaymentTransactionObserver&quot; are greyed out (it does not turn purple like the &quot;UIViewController&quot; does). Does anyone know what to do?</p>
  <p>Thanks in advance!</p>