class ScanNFCTag: NFCTagReaderSessionDelegate {

import CoreNFC

var session: NFCTagReaderSession?

func scanNFCTag(sender: UIButton!) {
     self.session = NFCTagReaderSession(pollingOption: .iso14443, delegate: self)
     self.session?.alertMessage = "Hold Your Phone Near the NFC Tag"
     self.session?.begin()
}

func tagReaderSessionDidBecomeActive(_ session: NFCTagReaderSession) {
    print("Session Begin!")
}

func tagReaderSession(_ session: NFCTagReaderSession, didInvalidateWithError error: Error) {
    print(error.localizedDescription)
}

func tagReaderSession(_ session: NFCTagReaderSession, didDetect tags: [NFCTag]) {
    if tags.count > 1{
        session.alertMessage = "More Than One Tag Detected, Please try again"
        session.invalidate()
    }
    
    let tag = tags.first!
    session.connect(to: tag) { (error) in
        if nil != error{
            session.invalidate(errorMessage: error?.localizedDescription ?? "")
        }
        if case let .miFare(sTag) = tag{
            let UID = sTag.identifier.map{ String(format:"%.2hhx", $0)}.joined()
            session.alertMessage = "Successfully linked tag to location"
            session.invalidate()
            DispatchQueue.main.async {
                print("NFC Identifer = ", "\(UID)")
               }
           }
       }
   }
}