I have a number of apps on the store, including several older paid apps. I'm releasing a new one that includes some of the functionality of the old ones via in-app purchase. I really don't want to double charge customers who have paid for the older apps. Is there a way, within my new app, to detect if a user has purchased my old apps, so that I can unlock the corresponding functionality for free?
In the form of an example:
Say I have three apps, A, B, and C.
A user has purchased App A at some time in the past.
Within App C, can I detect that the user has purchased App A in the past, and unlock some functionality accordingly?
I know with custom URL schemes you can string some of this together, but there is no guarantee that the user still has the older apps installed. Or, if they do, there is no guarantee that they would run an update on them so I could add custom URL schemes. Are there other, more elegant, ways to do this? For example are there any StoreKit methods for detecting installs on a per-publisher basis? Or is there a way to do it using the new identifierForVendor
stuff with iOS 7?
Any advice would be much appreciated. Thanks.