Question

I am developing an application where I have a section only for paid users where they purchase for the section using the in-app purhcase system in iOS. I know that I need to keep track of the purchase history myself, and this is where the problem begins. I have a database and I am capable of storing users in my database, with a web service interface. How can I create a system where a URL is pinged only when a user has made the purchase.

As an example, I have the URL:

http://example.com/registerUserPremium/userid=123456

How can I get this to be called only when a purchase is made? The most elegant way seems like Apple pinging the URL with a special user ID upon purchase, but I can’t find a way of doing it. It is obviously not a solution to make the user call that URL within the app, as it can be cracked/pirated. What is a good way of providing such a mechanism that is piracy-proof. My service is web-based, so if I can get this part done, the rest relies on my server-side mechanism (the user will just send a special key that is stored in its keychain, to the server) so I’ll be able to finish the project. In short, I need a way to call a URL only when a purchase is made. What are some possible solutions?

Thanks,

Can.

Answer 1

I see two solutions:

1. “Server product model” (doc): the appstore contact your servers every time a user makes a purchase. In this case you have all of the information right away.

2. “Builtin product model” (same doc) in which the application gets the receipt from the appstore. In this latter case you can contact your server special URL, providing the receipt information, and the server can verify that the receipt has not been tampered with asking the app store to verify (it’s a simple post, see here).