Apple's document does not seem to mention this. So if user cancels an auto-renewable subscription purchased during the free trial period, how do we detect?
In appstore receipt JSON there is this field: is_trial_period. But I think this is for indication of whether the free trial period is over.
The only thing I can think of is this NSBundle.mainBundle().appStoreReceiptURL?.path and if this is nil than that will indicate the user has not subscribed or cancel within the free trial period. But for sandbox testing, there is no way to do a cancel during free trial period to test this scenario.
Does anyone have a solid knowledge of this?
In order to support auto-renewing subscriptions, your app needs to periodically submit the app receipt obtained from NSBundle.mainBundle().appStoreReceiptURL?.path to Apple's receipt validation service.
Contained in the JSON response from this service is the latest_receipt_info array.
By examining this array you will be able to determine the currently active subscription(s).
If a user turns off auto-renewal before the expiration of the free trial then latest_receipt_info won't contain a purchase with an expires_date after the free trial end date
This means, that strictly speaking, you can't "detect a cancellation" as there is no "cancellation"; there just isn't a renewal at the end of the free trial period.