Designs for re-downloading an item with iOS In App Purchase that was free at download, but was changed to a non-consumable item later

Sorry for the long post.

I have an iOS app that sells non-consumable InAppPurchase items. I have free items, which are handled by the content server, which just skips the Apple receipt confirmation and starts the download. Both free and non-free items are stored the same way content-server wise, only a Boolean attribute sets them apart.

The problem is, I would have an item for free for a limited time, and then switch the item to non-free, thus requiring a receipt after that time. It all goes wrong when someone uninstalls the app, erasing the item and re-installs thinking they can just download it again for free, but they can't since its been set to non-free.

I would like the people who downloaded while it was free to be able to download after the item is set to non-free, the only way to do this that I can think of is hold the purchase information on the content s开发者_JAVA百科erver and a way to identify each request to a user somehow.

Is there any way to do this? Does anyone have experience in doing something like this and is willing to share it? Thanks in advance.

You will need to request any kind of identification from users, when getting the free item. Use this to get their e-mail address, Facebook/Twitter credentials, etc.

It's the only way to allow the user to recover their purchases later on, if they were not done using in app purchase.

You should let the user know that only by entering some ID, it will be possible to restore the purchases that weren't done via IAP.