updatedTransactions.swift

func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
        for transaction in transactions {
            guard let productType = ProductType(rawValue: transaction.payment.productIdentifier) else {fatalError()}
            switch transaction.transactionState {
            case .purchasing:
                self.delegate?.inAppLoadingStarted()
            case .purchased:
                SKPaymentQueue.default().finishTransaction(transaction)
                self.updateSubscriptionStatus()
                self.isSubscriptionAvailable = true
                self.delegate?.inAppLoadingSucceded(productType: productType)
            case .failed:
                if let transactionError = transaction.error as? NSError,
                    transactionError.code != SKError.paymentCancelled.rawValue {
                    self.delegate?.inAppLoadingFailed(error: transaction.error)
                } else {
                    self.delegate?.inAppLoadingFailed(error: InAppErrors.noSubscriptionPurchased)
                }
                SKPaymentQueue.default().finishTransaction(transaction)
            case .restored:
                SKPaymentQueue.default().finishTransaction(transaction)
                self.updateSubscriptionStatus()
                self.isSubscriptionAvailable = true
                self.delegate?.inAppLoadingSucceded(productType: productType)
            case .deferred:
                self.delegate?.inAppLoadingSucceded(productType: productType)
            }
        }
    }