我错过了什么？？展开时发现致命错误意外 nil

Question

@IBOutlet var txtusername: UITextField!
@IBOutlet var txtpassword: UITextField!

@IBAction func SigninTapped(sender: UIButton)
{
   var username:NSString = txtusername.text
    var password:NSString = txtpassword.text
  if (self.txtusername.text.isEmpty)
    {

        (UIAlertView(title: "Fields cant be empty", message: "Please Enter email id and password",
            delegate: nil, cancelButtonTitle: "OK").show())
        return
    }
    else if (range==nil)
    {
        (UIAlertView(title: "Invalid Email Id", message: "Please enter correct email id", delegate: nil, cancelButtonTitle: "OK").show())
        return
    }
    else if (txtpassword.text == ""  )
    {

        var alertView:UIAlertView = UIAlertView()
        alertView.title = "Failed!"
        alertView.message = "Please enter Password"
        alertView.delegate = self
        alertView.addButtonWithTitle("OK")
        alertView.show()
        return
    }
    else
    {
        var url:NSURL = NSURL(string:"http://192.168.0.31:8097/api/user/GetValidateUser" + "/" + username + "/" + txtpassword.text)!

        var err:NSError?
        var request:NSMutableURLRequest = NSMutableURLRequest(URL: url)
        request.HTTPMethod = "GET"
        request.addValue("application/json", forHTTPHeaderField: "Content-Type");
        request.addValue("application/json", forHTTPHeaderField: "Accept");
        var reponseError: NSError?
        var response: NSURLResponse?
        var urlData: NSData? = NSURLConnection.sendSynchronousRequest(request, returningResponse:&response, error:&reponseError)


        if ( urlData != nil )
        {
            let res = response as NSHTTPURLResponse!;

            var responseData:NSString  = NSString(data:urlData!, encoding:NSUTF8StringEncoding)!
            NSLog("Response code: %ld", res.statusCode);
            //var   message :String = "Valid user"
            if (res.statusCode == 200)
            {
                if(responseData != "\"Valid user\"")
                {
                    var alertView:UIAlertView = UIAlertView()
                    alertView.title = "Failed"
                    alertView.message = responseData
                    alertView.delegate = self
                    alertView.addButtonWithTitle("OK")
                    alertView.show()
                    return;
                }
                //Get the address book reference
                //GabbersController().GetAddressBook()

                //  var alertView:UIAlertView = UIAlertView()
                //   alertView.title = "Sign in Message"
                //  alertView.message = responseData
                //  alertView.delegate = self
                //  alertView.addButtonWithTitle("OK")
                //  alertView.show()
            }

            else {
                var alertView:UIAlertView = UIAlertView()
                alertView.title = "Failed"
                alertView.message = responseData;
                if let error = reponseError {
                    alertView.message = (error.localizedDescription)
                }
                alertView.delegate = self
                alertView.addButtonWithTitle("OK")
                alertView.show()
            }


        }

        else {
            var alertView:UIAlertView = UIAlertView()
            alertView.title = "Failed"
            alertView.message = "Connection failure";
            if let error = reponseError {
                alertView.message = (error.localizedDescription)
            }
            alertView.delegate = self
            alertView.addButtonWithTitle("OK")
            alertView.show()


        }
        //self.performSegueWithIdentifier:@"Goto__Gabbers" sender:self;

    }


}

对于上面的代码，我遇到了突然的错误，因为我认为我可能错过了参考出口，删除了现有的参考出口，并在我运行应用程序时在我的故事板中再次创建了同样的错误，但没有得到我实际上错过的内容。它第一次执行得很好，但后来却没有，抛出致命的意外 nil 错误，谁能告诉我这里到底错过了什么。

这是我得到的确切错误：

致命错误：在展开可选值时意外发现 nil

贴出我的完整代码

Answer 1

根据 Swift1.2，您可以执行以下操作。

@IBOutlet var txtusername: UITextField!
@IBOutlet var txtpassword: UITextField!

@IBAction func SigninTapped(sender: UIButton)
{
   if let userName = txtusername.text as? String, let password = txtpassword.text as? String {

    var url:NSURL = NSURL(string:"http://192.168.0.31:8097/api/user/GetValidateUser" + "/" + userName + "/" + password)!
    var err:NSError?
   }
}

Answer 2

此时txtusername.text 和txtpassword.text 可能是nil。

你必须检查这两个值是否都不为零，然后你可以做var url:NSURL = NSURL(string:"http://192.168.0.31:8097/api/user/GetValidateUser/\(txtusername.text)/\(txtpassword.text)")!