SwiftyStoreKit - How to properly restore auto renewable subscriptions?

Question

So I have a really basic concept of auto-renewable subscriptions in the app which unlocks PRO functionality. I also have a non-consumable purchase which is a "one-time purchase subscription" which unlocks the PRO functionality once and forever.

What I can't wrap my head around is, when I call restorePurchases (using SwiftyStoreKit) it brings in all purchases that were ever made by a user. Those may include multiple purchases of the same subscription which were expired long ago.

What I do next is I call a verifyPurchase method on each of those restored purchases and that method checks expiration date of each subscription that was ever purchased and if it is expired - it takes away the PRO from the user by clearing keychain (as it thinks that the current subscription got expired):

  case .expired(let expiryDate, let items):
             log.info("Subscription has expired on \(expiryDate)")
             log.debug(items)
             self.activeSubscription = nil
             self.clearStore()
             seal.reject(SubscriptionServiceError.expired(on: expiryDate))
  }

So what currently happens in my app is even if a user has an active subscription, if he or she tries to restorePurchases, there is a chance that verifyPurchase last purchase to verify would be an expired subscription, resulting in a canceled PRO version of the app for the user, even with an active subscription on board.

What would be the best practice to avoid this mistake and always verify the one and only right subscription?

Answer 1

From the SwiftyStoreKit docs:

let purchaseResult = SwiftyStoreKit.verifySubscription(
        ofType: .autoRenewable, // or .nonRenewing (see below)
        productId: productId,
        inReceipt: receipt)

    switch purchaseResult {
    case .purchased(let expiryDate, let items):
        print("\(productId) is valid until \(expiryDate)\n\(items)\n")
    case .expired(let expiryDate, let items):
        print("\(productId) is expired since \(expiryDate)\n\(items)\n")
    case .notPurchased:
        print("The user has never purchased \(productId)")
    }

It looks like you would pass in the product Id to determine if a specific subscription is still active.

You probably don't want to do this on every app launch so you should cache the result somewhere - all you need is probably the expiration date.