Swift: NFCError Code=202 "Session is invalidated unexpectedly"

user_2811242 0
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I'm trying to use NFC. I followed those steps:

  • Enabled NFC in the AppID configuration App ID Config

  • Created a provisioning profile and installed it Provisioning

  • Added NFC capability to the target NFC target NFC target code

  • Added the privacy description in the plist file Plist

After this I imported CoreNFC and implemented those code:

@available(iOS 11.0, *)    
    extension EventPreviewViewController: NFCNDEFReaderSessionDelegate {
            func readerSession(_ session: NFCNDEFReaderSession, didInvalidateWithError error: Error) {
                let alert = UIAlertController.withOkButton(andTitle: NSLocalizedString("TitleWarning"), andText: NSLocalizedString("ErrorNFCInvalidate"), okHandler: nil)
                self.present(alert, animated: true, completion: nil)
            }

            func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {
                // TODO
            }
        }


class EventPreviewViewController: UITableViewController {
@available(iOS 11.0, *)
var nfcSession: NFCNDEFReaderSession {
        return NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: true)
    }

    @IBAction func startAccess(_ sender: UIButton) {
    if #available(iOS 11.0, *) {
                    nfcSession.begin()
                } else {
                    let alert = UIAlertController.withOkButton(andTitle: NSLocalizedString("TitleWarning"), andText: NSLocalizedString("ErrorNFCUnsupported"), okHandler: nil)
                    self.present(alert, animated: true, completion: nil)
                }
    }
}

Why I keep getting "Error Domain=NFCError Code=202 "Session is invalidated unexpectedly" UserInfo={NSLocalizedDescription=Session is invalidated unexpectedly}"?

nfc swift ios
2 Answers
user_9273330

I am not sure but below line causing this error Session is invalidated unexpectedly

When I was worked with CoreNFC, I was faced similar kind of issue. Fix it by defining as property

let nfcSession = NFCNDEFReaderSession(delegate: self, queue: DispatchQueue(label: "queueName", attributes: .concurrent), invalidateAfterFirstRead: true)

I suggest you need to define nfcSession as property.

var nfcSession: NFCNDEFReaderSession?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    self.nfcSession = NFCNDEFReaderSession(delegate: self, queue: DispatchQueue.global(qos: .background), invalidateAfterFirstRead: false)
    self.nfcSession?.begin()
    return true
}

Update:

You can define a property for iOS 11 like below.

@available(iOS 10.0, *)
    var session: NFCNDEFReaderSession?
user_50365860
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