问题
I have an app that uses non-renewable in-app purchase products. Today I am thinking of releasing some 100 in-app Promo Codes for my initial users.
The in-app purchases work as expected in the app, but I'm unable to figure out what kind of check I need to do on app if the user has redeemed promo-code on App Store already.
ie., How do I check whether a user has redeemed a in-app purchase promo-code when they return to my app?
Edit: I also need the receipt to set an expiry date for the purchased product based on its purchase date. How do I get this receipt?
来源：https://stackoverflow.com/questions/41931584/ios-detecting-promo-code-in-app-purchases