问如何在OS中快速使用.isempty

EN

class InsideViewController: NSViewController {

    @IBOutlet var userNametext: NSTextField!
    @IBOutlet var passwordtext: NSSecureTextField!
    @IBOutlet var conformpasswordtext: NSSecureTextField!


    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override var representedObject: AnyObject? {
        didSet {
            // Update the view, if already loaded.
        }
    }

    @IBAction func SignUpButton(sender: NSButton) {
        let userName = userNametext.stringValue
        let userPassword = passwordtext.stringValue
        let userPasswordcon = conformpasswordtext.stringValue

        NSUserDefaults.standardUserDefaults().setObject(userName, forKey: "username")
        NSUserDefaults.standardUserDefaults().setObject(userPassword, forKey: "userpassword")
        NSUserDefaults.standardUserDefaults().synchronize()

        if (userNametext.isempty)
    }

}