Using touch ID

touchID.swift

    import LocalAuthentication

    ...

    private func authenticateUser() {
        let context = LAContext()
        var error: NSError?
        
        if context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) {
            let reason = "Identify yourself!"
            
            context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason) {
                [unowned self] success, authenticationError in
                
                DispatchQueue.main.async {
                    if success {
                        debugPrint("authorized!")
                    } else {
                        let ac = UIAlertController(title: "Authentication failed", message: "Sorry!", preferredStyle: .alert)
                        ac.addAction(UIAlertAction(title: "OK", style: .default))
                        self.present(ac, animated: true)
                    }
                }
            }
        } else {
            let ac = UIAlertController(title: "Touch ID not available", message: "Your device is not configured for Touch ID.", preferredStyle: .alert)
            ac.addAction(UIAlertAction(title: "OK", style: .default))
            present(ac, animated: true)
        }
    }