title: Already purchased subscriptions in StoreKit
body: <p>I am using renewable subscriptions in app purchases in an iOS app.
  When a user attempts to purchase a subscription that they already have paid for a message is displayed from iTunes "You're currently subscribed to this". </p>
  
  <p>How I can detect when this event has occurred so that I can process the transaction and grant access to my app.</p>
  
  <p>In the paymentQueue:updatedTransactions: method of the observer it is coming through as a SKPaymentTransactionStateFailed. How do I distinguish between this type of failure and other failures such as the user pressing the cancel buttons?</p>
  
  <p>Do I submit the transaction that is returned or do I need to call restorePreviousTransactions.</p>
  
  <p>In the Apple documents it states "If the user attempts to purchase a non-consumable product or a renewable subscription they have already purchased, your application receives a regular transaction for that item, not a restore transaction. However, the user is not charged again for that product. Your application should treat these transactions identically to those of the original transaction."</p>