从警报textField获得价值

Question

我目前正在尝试从Swift 3的警报框中获取值。

下面的代码用于提示警报并保存数据，但是，在回调数据和操作数据时遇到麻烦，因此它只是一个基本字符串。

 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)
    }

此方法在这里称为：

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

我正在尝试调用它，并将其分配为以下字符串之间：

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

但是，这给了我输出：

http://Optional():3000/unLock

当我尝试打印它时。

朝正确方向的任何轻推都将不胜感激。 新增课程：

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()

    }
   }

谢谢。

Answer 1

该值是可选的：

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

尝试：

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

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