applepay.swift

//1. Check if the PKPaymentAuthorizationViewController can make payments
if PKPaymentAuthorizationViewController.canMakePayments(usingNetworks: paymentNetworks) {
      // develop your payment request
      let request = PKPaymentRequest()
      request.merchantIdentifier = "merchant.yourmerchantid" //add more info to the payment request as needed

      //2. Then present the Apple Pay authorizationViewController
      let authorizationViewController = PKPaymentAuthorizationViewController(paymentRequest: request)
      if let viewController = authorizationViewController {
          viewController.delegate = self
          self.present(viewController, animated: true, completion: nil)
       }
}

//3. handle auth completion
public func paymentAuthorizationViewController(_ controller: PKPaymentAuthorizationViewController, didAuthorizePayment payment: PKPayment, completion: ((PKPaymentAuthorizationStatus) -> Void)) {
       completion(PKPaymentAuthorizationStatus.success)
}
    
public func paymentAuthorizationViewControllerDidFinish(_ controller: PKPaymentAuthorizationViewController) {
       controller.dismiss(animated: true, completion: nil)
}