> For the complete documentation index, see [llms.txt](https://docs.payments.thalescloud.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payments.thalescloud.io/nfc-wallet-sdk-ios/implement-nfc-wallet/make-payments/implement-contactless-payment/full-implementation-example.md). # Full implementation example Use this code sample to understand how the previous steps fit together. It initiates contactless payment from: * **Double-click** (`NFCWindowSceneEvent.presentation`) * **Field detect** (`NFCWindowSceneEvent.readerDetected`) {% hint style="info" %} This sample assumes you already reviewed the individual implementation steps. {% endhint %} ### Full source code {% code title="SceneDelegate.swift" expandable="true" %} ```swift class SceneDelegate: UIResponder, UIWindowSceneDelegate { var window: UIWindow? var rootViewController: UIViewController? let session = ContactlessPaymentSession() // if double-click or field detect is detected, set to true var isDefaultPaymentApp = false // done for iOS 18 where it might need to start emulation on field-detect var isPaymentOngoing = false // to support initiate contactless payments by double-click or field-detect action when application is not running: func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) { // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`. // If using a storyboard, the `window` property will automatically be initialized and attached to the scene. // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead). guard let windowScene = (scene as? UIWindowScene) else { return } let storyboard = UIStoryboard(name: "Main", bundle: nil) let landingVC = storyboard.instantiateViewController(identifier: "LandingSB") let window = UIWindow(windowScene: windowScene) window.rootViewController = landingVC window.makeKeyAndVisible() self.window = window rootViewController = landingVC // set to false each time when it entered isDefaultPaymentApp = false if #available(iOS 17.4, *) { if let nfcEvent = connectionOptions.nfcEvent { switch nfcEvent { case .presentation: // set to true as only been triggered when is default payment application isDefaultPaymentApp = true startPayment() case .readerDetected: // set to true as only been triggered when is default payment application isDefaultPaymentApp = true handleFieldDetect(withCurrentVC: window.rootViewController) @unknown default: break } } } } func sceneDidEnterBackground(_ scene: UIScene) { // set to false each time when it exits, as you may set another app as default isDefaultPaymentApp = false // Called as the scene transitions from the foreground to the background. // Use this method to save data, release shared resources, and store enough scene-specific state information // to restore the scene back to its current state. if #available(iOS 17.4, *) { Task { // default payment app, after session started, will accept APDU and complete payment in background // this is to cancel it while App goes to the background. // This action is also recommended when App moves to different screen than the payment screen etc. await session.cancel() } } } } extension SceneDelegate: NFCWindowSceneDelegate { @available(iOS 17.4, *) // to support initiate contactless payments by double-click or field-detect action when application is background or foreground: func windowScene(_ windowScene: UIWindowScene, didReceiveNFCWindowSceneEvent event: NFCWindowSceneEvent) { switch event { case .presentation: isDefaultPaymentApp = true startPayment() case .readerDetected: isDefaultPaymentApp = true handleFieldDetect(withCurrentVC: rootViewController) @unknown default: break } } } extension SceneDelegate { // prompt the UI to indicate start the payment by double click func displayAlertWithDoubleClickStartPayment(withCurrentVC currentVC: UIViewController?) { let alertController = UIAlertController(title: "Please Double-click to start the payment", message: nil, preferredStyle: .alert) alertController.addAction( UIAlertAction(title: "OK", style: .default) ) currentVC?.present(alertController, animated: false) } // return true if require double-click prompt @available(iOS 17.4, *) func handleFieldDetect(withCurrentVC currentVC: UIViewController?){ // to tell if it is a normal field detect or we consider as readerDetect for ongoing paymentSession // only for iOS 18 + if #available(iOS 18, *), isPaymentOngoing { // it is iOS 18 + where ongoing payment had received readerDetect event Task { try await self.session.startEmulation() } } else { // handle field detect normally on following scenario: // - iOS 17.4+, regardless payment ongoing OR not ongoing. // - iOS 18.x, payment not ongoing. let biometricType = biometricType() // start payment directly for fingerprint if biometricType == .touchID { startPayment() } else { displayAlertWithDoubleClickStartPayment(withCurrentVC: currentVC) } } } func startPayment(withDigitalCardID digitalCardID: String? = nil) { Task { // initialize the SDK try await TSHPay.shared.configure(withVerificationMethod: .userPresence) if #available(iOS 17.4, *) { // indicate payment is on-going, it required for field-detect and iOS 18 isPaymentOngoing = false // checking whether is default payment app and check presentmentIntent whether is valid if !isDefaultPaymentApp, !PresentmentIntentWrapper.isValid() { do { // Not detecting default payment app behavior, we try to obtain presentmentIntentAssertion try await PresentmentIntentWrapper.acquire() print("presentmentIntent assertion acquired \(PresentmentIntentWrapper.isValid())") } catch { // failed... either due to error or the cool-down // we have to directly start emulation, at least we wont get app re-directed } } if let digitalCardID { print("StartPayment:: with digitalCardID") await session.startPayment(withDigitalCardID: digitalCardID) } else { print("StartPayment:: without digitalCardID") await session.startPayment() } for await event in await session.eventStream { switch event { case .authenticationRequired(let action): print("StartPayment:: authenticationRequired") Task { action.proceed() } case .authenticationCompleted: print("StartPayment:: authenticationCompleted") isPaymentOngoing = true // Scenerio A: change card // if want to startEmulation at Event .authenticationCompleted // try await session.startEmulation() break case .posConnected: print("StartPayment:: posConnected") await session.setAlertMessage("POS Connected") // if application do not acquire NFCPresentmentIntentAssertion, it's not able call startEmulation() in this event. try await session.startEmulation() break case .posDisconnected: print("StartPayment:: posDisconnected") await session.setAlertMessage("POS Disconnected") case .transactionCompleted(let context): print("StartPayment:: transactionCompleted") await session.setAlertMessage("Transaction Completed") // display to user displayTransactionContext(context) case .errorEncountered(let error): switch (error as? ContactlessPaymentSession.Error) { case .cancelled: // End-user cancel the transaction. break case .maxSessionDurationReached: // Display message to end-user that transaction has timed out. break case .nfcPermissionNotAccepted: // Display message to end-user that permission is not allowed. break case .systemEligibilityFailed: // Display message to end-user that system is not eligible for contactless payment. // e.g. Apple ID or device location is not in EEA. break case .noPaymentKeys: // Replenishment is required. Refer to Replenishment guide. break case .noDefaultCard: // Default card should be set before transaction. break case .keychainError: // Display error message to end-user break case .apduFailure(let reason): // Retry again break case .unknown(let underlying): // Display error message to end-user break case .transmissionError: // Error encountered in APDU exchange between device and POS reader break case .sessionInvalidated: // The card session has been invalidated by system break case .deviceEnvironmentUnsafe(_): // Device Environment Unsafe error break case .setDefaultCardFailure: // Error encountered when attempting to set the provided Digital Card ID as the default card during the `startPayment(withDigitalCardID:)` API call. break case .invalidDigitalCardID: // Digital Card ID provided is invalid when ``startPayment(withDigitalCardID:)`` break case .authenticationExpired: // Error encountered when payment is made after the authentication has been validated. break case .posNotSupported: // Error encountered when POS does not have selected AID in the list. break case .cardNotSupported: // The card is not supported for contactless payment. break case .cardNotActive: // The card selected is not active. break case .authenticationFailed: // Error encountered when the authentication fails. break case .authenticationKeyInvalidated(let underlying): // Authentication key is invalidated because the device passcode is either turned off or reset, triggering a security reset. // SDK will automatically wipe the stored credentials when this error occurs. // App must guide user through the re-enrollment process. // Post a notification to reload the card. showAlert(message: underlying.localizedDescription) { NotificationCenter.default.post(name: .didReceiveRequestForReloadCard, object: nil) } break case .biometricNotEnrolled(let message): // Displays a message to end user to perform biometric enrollment. showAlert(message: "\(message)") break @unknown default: break } @unknown default: fatalError("fixme: encountered unknown case") } } isPaymentOngoing = false } else { // Fallback on earlier versions. let alertController = UIAlertController(title: "Please use the device with iOS 17.4 or above", message: nil, preferredStyle: .alert) alertController.addAction( UIAlertAction(title: "OK", style: .default) ) rootViewController?.present(alertController, animated: false) } } } func biometricType() -> LABiometryType { let authContext = LAContext() if #available(iOS 11, *) { authContext.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: nil) return authContext.biometryType } return LABiometryType.none } } ``` {% endcode %} --- # Agent Instructions This documentation is published with GitBook. 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