title: SKPaymentTransaction transactionState does not become SKPaymentTransactionStatePurchased after purchasing
body: <p>I've implemented the In-App payments like described in the Apple Documents about IAP, but when I try them in Sandbox mode, the 'transactionState' will never get changed to SKPaymentTransactionStatePurchased. (It stays on SKPaymentTransactionStatePurchasing forever.)</p>
  
  <p>Does anybody know what went wrong?</p>
  
  <pre><code>- (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions
  {
      for (SKPaymentTransaction *transaction in transactions)
      {
          NSLog(@"%ld", transaction.transactionState);
          switch (transaction.transactionState)
          {
              case SKPaymentTransactionStatePurchased:
                  [self completeTransaction:transaction];
                  break;
              case SKPaymentTransactionStateFailed:
                  [self failedTransaction:transaction];
                  break;
              case SKPaymentTransactionStateRestored:
                  [self restoreTransaction:transaction];
              default:
                  break;
          }
      }
  }
  
  - (void)completeTransaction:(SKPaymentTransaction *)transaction
  {
      [self recordTransaction:transaction];
      [self provideContent:transaction.payment.productIdentifier];
      [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
  }
  
  - (void)failedTransaction:(SKPaymentTransaction *)transaction
  {
      if (transaction.error.code != SKErrorPaymentCancelled) {
          [NSAlert alertWithError:transaction.error];
      }
      [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
  }
  
  - (void)restoreTransaction:(SKPaymentTransaction *)transaction
  {
      [self recordTransaction:transaction];
      [self provideContent:transaction.originalTransaction.payment.productIdentifier];
      [[SKPaymentQueue defaultQueue] finishTransaction:transaction];
  }
  
  - (void)recordTransaction:(SKPaymentTransaction *)transaction
  {
      NSLog(@"Record Transaction...");
      // ToDo: Implement 'recordTransaction'.
  }
  
  - (void)provideContent:(NSString *)productIdentifier
  {
      NSLog(@"Provide Content");
      // ToDo: Implement 'provideContent'.
  }
  </code></pre>