i have a paid app on the app store which i have changed to free woth inapp purchase. Those users who have purchased the paid app, i want them to get the inapp purchases for free as the app has the same feature with existing features as inapp purchase and exisiting users have already paid for the full version. How can i achieve this?
Would changing the fee (to zero) for in app purchase in a new release not make it ?
But how do i check if it is an existing user?
Have you released the free version w/IAP yet? If not, release an update to the paid app version that includes a marker in either user defaults, or the keychain.
Then release the free/IAP version with a check for that marker. If it finds the marker, enable the IAP items automatically. If not, provide the option to IAP.
The established technique is to examine the receipt of the app. It will have a field in it entitled original_application_version. That will indicate the 'Build' number (unfortunately not the Version number!!!) of the app that the user originally purchased. In your 'new' free app you use a different Build number - like 4.1 then 4.2 then 4.3. You use that Build number to separate the paid purchases from the free purchases.
(iOS - Build number; for Mac Apps it's the version number)