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import StripePaymentSheet

class MyCheckoutVC: UIViewController {
  func didTapCheckoutButton() {
    let intentConfig = PaymentSheet.IntentConfiguration(
      mode: .payment(amount: 1099, currency: "USD")
    ) { [weak self] paymentMethod, shouldSavePaymentMethod, intentCreationCallback in
      self?.handleConfirm(paymentMethod, shouldSavePaymentMethod, intentCreationCallback)
    }
    var configuration = PaymentSheet.Configuration()
    configuration.returnURL = "your-app://stripe-redirect" // Use the return url you set up in the previous step
    let paymentSheet = PaymentSheet(intentConfiguration: intentConfig, configuration: configuration)
  }

  func handleConfirm(_ paymentMethod: STPPaymentMethod, _ shouldSavePaymentMethod: Bool, _ intentCreationCallback: @escaping (Result<String, Error>) -> Void) {
    // ...explained later
  }
}

class MyCheckoutVC: UIViewController {
  func didTapCheckoutButton() {
    // ...
    paymentSheet.present(from: self) { result in
      switch result {
        case .completed:
          // Payment completed - show a confirmation screen.
        case .failed(let error):
          print(error)
          // PaymentSheet encountered an unrecoverable error. You can display the error to the user, log it, etc.
        case .canceled:
          // Customer canceled - you should probably do nothing.
      }
    }
  }
}

class MyCheckoutVC: UIViewController {
  // ...

  func handleConfirm(_ paymentMethod: STPPaymentMethod, _ shouldSavePaymentMethod: Bool, _ intentCreationCallback: @escaping (Result<String, Error>) -> Void) {
    // Make a request to your own server, passing paymentMethod.stripeId and shouldSavePaymentMethod, and receive a client secret or an error..
    let myServerResponse: Result<String, Error> = ...
    switch myServerResponse {
    case .success(let clientSecret):
      // Call the `intentCreationCallback` with the client secret
      intentCreationCallback(.success(clientSecret))
    case .failure(let error):
      // Call the `intentCreationCallback` with the error
      intentCreationCallback(.failure(error))
    }
  }
}