title: Displaying progress indicator while in-app purchase (or restored purchase) on iPhone is being processed
body: <p>How do I show a progress indicator during processing of in-app purchase on iPhone? I know how to display progress/activity indicator itself, but I need to know when to start it. If I start it right after calling </p>
  
  <pre><code>[[SKPaymentQueue defaultQueue] addPayment:payment]; 
  </code></pre>
  
  <p>method I will see the indicator when user is presented with iTunes account password prompt. I would like to start the progress when this prompt has been already passed. Also, the same thing for restoring completed transactions:</p>
  
  <pre><code>[[SKPaymentQueue defaultQueue] restoreCompletedTransactions]; 
  </code></pre>
  
  <p>I tried to hook up the indicator to SKPaymentTransactionStatePurchasing state within </p>
  
  <pre><code>paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions
  </code></pre>
  
  <p>but still get it started before the password prompt. Any suggestions?</p>