In App Purchase finished outside of an iPhone app

I am implementing an in app purchase subscription model.

Let's say I have an iPhone 3 user which starts the whole purchase process from my application and then exits the application only to continue and fill his app store credentials outside of my app until he is done with the purchase.

How can my app know t开发者_如何学编程hat the transaction was made upon launch? Also in case I do get this info how can I tell it is not an old purchase for an old subscription period which has already expired?

And last but not least in case the device supports multitasking and the purchase was finished while my app was in the background how will I get notified upon returning to the foreground?

Thanks

Roi

Have you read Apple's Documentation - In App Purchase Programming Guide? I believe it answers all your questions.

The - (void)recordTransaction:(SKPaymentTransaction *)transaction method takes care of most of your pains.

Once you properly implement this method,you would just have to check whether the inApp purchase is done.Rest is taken care of by the payment methods.

Thanks