UIViewController.swift

class UIViewController: UIViewController, PKPaymentAuthorizationViewControllerDelegate {
  @objc private func applePayButtonTapped(sender: UIButton) {
      // Cards that should be accepted
      let paymentNetworks:[PKPaymentNetwork] = [.amex,.masterCard,.visa]

      if PKPaymentAuthorizationViewController.canMakePayments(usingNetworks: paymentNetworks) {
          let request = PKPaymentRequest()

          request.merchantIdentifier = "merchant.com.shiningdevelopers"
          request.countryCode = "CA"
          request.currencyCode = "CAD"
          request.supportedNetworks = paymentNetworks
          request.requiredShippingContactFields = [.name, .postalAddress]
          // This is based on using Stripe
          request.merchantCapabilities = .capability3DS

          let tshirt = PKPaymentSummaryItem(label: "T-shirt", amount: NSDecimalNumber(decimal:1.00), type: .final)
          let shipping = PKPaymentSummaryItem(label: "Shipping", amount: NSDecimalNumber(decimal:1.00), type: .final)
          let tax = PKPaymentSummaryItem(label: "Tax", amount: NSDecimalNumber(decimal:1.00), type: .final)
          let total = PKPaymentSummaryItem(label: "Total", amount: NSDecimalNumber(decimal:3.00), type: .final)
          request.paymentSummaryItems = [tshirt, shipping, tax, total]

          let authorizationViewController = PKPaymentAuthorizationViewController(paymentRequest: request)

          if let viewController = authorizationViewController {
              viewController.delegate = self

              present(viewController, animated: true, completion: nil)
          }
      }
  }

  func paymentAuthorizationViewController(_ controller: PKPaymentAuthorizationViewController, didAuthorizePayment payment: PKPayment, handler completion: @escaping (PKPaymentAuthorizationResult) -> Void) {
    // Let the Operating System know that the payment was accepted successfully
    completion(PKPaymentAuthorizationResult(status: .success, errors: nil))
  }

  func paymentAuthorizationViewControllerDidFinish(_ controller: PKPaymentAuthorizationViewController) {
     // Dismiss the Apple Pay UI
     dismiss(animated: true, completion: nil)
  }
}