I'm implementing an iOS app with non-renewing subscription. Not much relevant information was available online; so I seek your guidance.
A use case which worries me the most is when a user purchased the subscription once and then immediately after purchase it again to extend the duration of service (see such scenario here). What if that user were to refund the first purchase, leaving the second one intact? Is this even possible in practice, or am I just too paranoid?
Assuming the above case is possible, my app will run into a problem because, as far as I know, verifyReceipt only returns the latest, good receipt (watch Managing Subscriptions with In-App Purchase in WWDC'12).
I find nowhere Apple provides relevant information about refunding policies.
(Auto-renewable subscription seems to rule out this case as a renewing action is taken care by iTunes automagically and it seems not possible to extend this type of subscription until iTunes allows it.)
verifyReceipt will not only return the latest good receipt, it will also tell you if the receipt you submitted for verification is good. So if you're concerned that a user may have cancelled* a transaction, then submit every receipt you're questioning.
*But what do you mean by "cancel" the first purchase? Do you mean when they tap "cancel" instead of "buy?" Well then the transaction won't go through and you won't even get a receipt.
Or do you mean when they request a refund? I don't know any other way they can cancel a purchase.
Edit:
If you're referring to refunds, there's no way for a developer to tell if a user has been issued a refund. The assumption is that Apple expects you to continue to deliver services to that user regardless of the fact that they received a refund. Your receipts will probably all verify correctly regardless of the status of a refund.