Get value from alert textField

Question

I'm currently trying to get a value from an alert box in swift 3.

The below code is used to prompt the alert and save the data, however, im having trouble with calling back the data and manipulating it so it's just a basic string.

 func presentAlert() {
        let alertController = UIAlertController(title: "IP?", message: "Please input your unique key:", preferredStyle: .alert)

        let confirmAction = UIAlertAction(title: "Confirm", style: .default) { (_) in
            if let field = alertController.textFields?[0] {
                // store it
                UserDefaults.standard.set(field.text, forKey: "userIP")
                UserDefaults.standard.synchronize()
            } else {
                // user did not fill field
                print("no input given")
            }
        }

        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { (_) in }

        alertController.addTextField { (textField) in
            textField.placeholder = "IP"
        }

        alertController.addAction(confirmAction)
        alertController.addAction(cancelAction)

        self.present(alertController, animated: true, completion: nil)
    }

This method is called here:

override func viewDidAppear(_ animated: Bool) {
        presentAlert()
    }

I'm trying to call it and assign it in between a string as:

let url_to_unlock:String = "http://\(UserDefaults.standard.value(forKey: "userIP")):3000/unLock"

However, this gives me the output:

http://Optional():3000/unLock

When I try to print it.

Any nudge in the correct direction would be greatly appreciated. Class Added:

class ViewController: UIViewController {

    func presentAlert() {
        let alertController = UIAlertController(title: "IP?", message: "Please input your unique key:", preferredStyle: .alert)

        let confirmAction = UIAlertAction(title: "Confirm", style: .default) { (_) in
            if let field = alertController.textFields?[0] {
                // store your data
                //this could be lock unique key name etc in future
                UserDefaults.standard.set(field.text, forKey: "userIP")
                UserDefaults.standard.synchronize()
            } else {
                // user did not fill field
                print("no input given")
            }
        }

        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { (_) in }

        alertController.addTextField { (textField) in
            textField.placeholder = "IP"
        }

        alertController.addAction(confirmAction)
        alertController.addAction(cancelAction)

        self.present(alertController, animated: true, completion: nil)
    }
    //view did appear for the alert
    override func viewDidAppear(_ animated: Bool) {
        presentAlert()
    }

    //to post to an /unLock it must be put in the URL


   // let url_to_unlock:String = "http://\(UserDefaults.standard.value(forKey: "userIP")):3000/unLock"
    //let url_to_lock:String = "http://\(textField):3000/Lock"

    let url_to_unlock:String = "http://10.73.195.218:3000/unLock"
    let url_to_lock:String = "http://10.73.195.218:3000/Lock"

    override func viewDidLoad() {
        super.viewDidLoad()

    }
    var Timestamp: String {
        return "\(NSDate().timeIntervalSince1970 * 1000)"
    }
    func un_lock()
    {
          print(url_to_unlock)
        let url:URL = URL(string: url_to_unlock)!
        let session = URLSession.shared

        let request = NSMutableURLRequest(url: url)
        request.httpMethod = "POST"
        request.cachePolicy = NSURLRequest.CachePolicy.reloadIgnoringCacheData

        let paramString = "data=unLocking at \(Timestamp)"
        request.httpBody = paramString.data(using: String.Encoding.utf8)

        let task = session.dataTask(with: request as URLRequest, completionHandler: {
            (
            data, response, error) in

            guard let _:Data = data, let _:URLResponse = response  , error == nil else {
                print("error")
                return
            }
            //for errors
            let dataString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
            print(dataString! )

        })

        task.resume()
    }

    func lock()
    {
        let url:URL = URL(string: url_to_lock)!
        let session = URLSession.shared

        let request = NSMutableURLRequest(url: url)
        request.httpMethod = "POST"
        request.cachePolicy = NSURLRequest.CachePolicy.reloadIgnoringCacheData

        let paramString = "data=Locking at \(Timestamp)"
        request.httpBody = paramString.data(using: String.Encoding.utf8)

        let task = session.dataTask(with: request as URLRequest, completionHandler: {
            (
            data, response, error) in

            guard let _:Data = data, let _:URLResponse = response  , error == nil else {
                print("error")
                return
            }
            //for errors
            let dataString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
            print(dataString! )

        })

        task.resume()

    }

    @IBAction func lock(_ sender: UIButton) {
        lock()
    }

    @IBAction func unLock(_ sender: Any) {
        un_lock()

    }
   }

Thank you.

Answer 1

The value for this is optional:

 // let url_to_unlock:String = "http://\(UserDefaults.standard.value(forKey: "userIP")):3000/unLock"

try:

let url = UserDefaults.standard.value(forKey: "userIP")!

let url_to_unlock:String = "http://\(url):3000/unLock"