Unable to call function after Apple Pay success SwiftUI

Question

I have Apple Pay implemented in my SwiftUI app and I'd like to call a function after payment status returns a success. However, when I try to call the function, I run into error "Type () cannot conform to View". Relevant code:

PaymentView.swift (SwiftUI view where Apple Pay button is displayed):

@StateObject var applePayModel = ApplePayModel()
//....code....//
var body: some View {
     PaymentButton(){
                    // Apple Pay Model
                    applePayModel.pay(clientSecret: PaymentConfig.shared.paymentIntentClientSecret)
                }
                
                if let paymentStatus = applePayModel.paymentStatus {
                    switch paymentStatus {
                    case .success:
                        postPaymentSetup() // trying to call this function!!
                        Text("Payment complete!")
                    case .error:
                        Text("Payment failed")
                    case .userCancellation:
                        Text("Payment canceled")
                    @unknown default:
                        Text("Unknown status")
                    }
                }
            }

ApplePayModel.swift

import Foundation
import Stripe
import PassKit

class ApplePayModel : NSObject, ObservableObject, STPApplePayContextDelegate {
    @Published var paymentStatus: STPPaymentStatus?
    @Published var lastPaymentError: Error?
    var clientSecret: String?

    func pay(clientSecret: String?) {
    self.clientSecret = clientSecret
    // Configure a payment request
    let pr = StripeAPI.paymentRequest(withMerchantIdentifier: "merchant.com.app", country: "US", currency: "USD")
    
    // You'd generally want to configure at least `.postalAddress` here.
    // We don't require anything here, as we don't want to enter an address
    // in CI.
    pr.requiredShippingContactFields = []
    pr.requiredBillingContactFields = []
    
    // Configure shipping methods
    pr.shippingMethods = []
    
    // Build payment summary items
    // (You'll generally want to configure these based on the selected address and shipping method.
    pr.paymentSummaryItems = [
        PKPaymentSummaryItem(label: "Widget)", amount: NSDecimalNumber(string: "0.00")),
        PKPaymentSummaryItem(label: "Merchant", amount: NSDecimalNumber(string: "0.00")),
    ]
    
    // Present the Apple Pay Context:
    let applePayContext = STPApplePayContext(paymentRequest: pr, delegate: self)
    applePayContext?.presentApplePay()
}


func applePayContext(_ context: STPApplePayContext, didCreatePaymentMethod paymentMethod: STPPaymentMethod, paymentInformation: PKPayment, completion: @escaping STPIntentClientSecretCompletionBlock) {
    // Confirm the PaymentIntent
    if (self.clientSecret != nil) {
        // Call the completion block with the PaymentIntent's client secret.
        completion(clientSecret, nil)
    } else {
        completion(nil, NSError())
    }
}

func applePayContext(_ context: STPApplePayContext, didCompleteWith status: STPPaymentStatus, error: Error?) {
    // When the payment is complete, display the status.
    self.paymentStatus = status
    self.lastPaymentError = error
    
}

}

ApplePayModel is an observable object so I know there should be a way to check when its paymentStatus has changed. Just haven't figured out a way yet. Any ideas?

Thanks!

EDIT:

Here's the function I'm trying to call, located in PaymentView.swift:

    func postPaymentSetup(){
    DataService.instance.updateUser(userID: currentUserID)
    // send notifications to seller
    AuthService.instance.getUserOnesignalID(forUserID: selectedSellerID) { onesignalID in
        OneSignal.postNotification(["contents": ["en": "Your payment has succeeded!"], "include_player_ids": ["\(onesignalID ?? "")"]])
    }
    showToast = true
    toastMessage = "Payment Completed ✅"
    isShowingSheet = false
    isShowingSheet_Reservation = false
    showSelectButton = false
    presentationMode.wrappedValue.dismiss()
}