IAPHelper3.swift

extension IAPHelper: SKPaymentTransactionObserver {
  
    public func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
        for transaction in transactions {
            switch (transaction.transactionState) {
            case .purchased:
                complete(transaction: transaction)
                break
            case .failed:
                fail(transaction: transaction)
                break
            case .restored:
                restore(transaction: transaction)
                break
            case .deferred, .purchasing:
                break
            @unknown default:
                fatalError()
            }
        }
    }
    
    // 구입 성공
    private func complete(transaction: SKPaymentTransaction) {
        deliverPurchaseNotificationFor(identifier: transaction.payment.productIdentifier)
        SKPaymentQueue.default().finishTransaction(transaction)
    }
    
    // 복원 성공
    private func restore(transaction: SKPaymentTransaction) {
        guard let productIdentifier = transaction.original?.payment.productIdentifier else { return }
        deliverPurchaseNotificationFor(identifier: productIdentifier)
        SKPaymentQueue.default().finishTransaction(transaction)
    }
    
    // 구매 실패
    private func fail(transaction: SKPaymentTransaction) {
        if let transactionError = transaction.error as NSError?,
            let localizedDescription = transaction.error?.localizedDescription,
            transactionError.code != SKError.paymentCancelled.rawValue {
            print("Transaction Error: \(localizedDescription)")
        }
        SKPaymentQueue.default().finishTransaction(transaction)
    }
    
    // 구매한 인앱 상품 키를 UserDefaults로 로컬에 저장
    private func deliverPurchaseNotificationFor(identifier: String?) {
        guard let identifier = identifier else { return }

        let dict: ProductInfo = [IAPProductKey.purchased: true,
                                 IAPProductKey.validated: false]
        UserDefaults.standard.setValue(dict, forKey: identifier)

        requestValidation(productId: identifier)
    }
}