ios - 取消 Segue 并显示警报 - Xcode

Question

我从这个网站得到教程:http://jamesleist.com/ios-swift-tutorial-stop-segue-show-alert-text-box-empty/

这是我当前的代码。它只是不工作，这会导致应用程序崩溃，因为如果任何字段为空，下一个 ViewController 就会崩溃。

import Foundation
import UIKit
import Darwin

class View3on3 : UIViewController, UITextFieldDelegate {


@IBOutlet weak var APTeams: UITextField!
@IBOutlet weak var APRounds: UITextField!
@IBOutlet weak var APBreakers: UITextField!

var AP1: String = String()
var AP2: String = String()
var AP3: String = String()


override func viewDidLoad()
{
    super.viewDidLoad()
    initializeTextFields()
}


func initializeTextFields()
{
    APTeams.delegate = self
    APTeams.keyboardType = UIKeyboardType.NumberPad

    APRounds.delegate = self
    APRounds.keyboardType = UIKeyboardType.NumberPad

    APBreakers.delegate = self
    APBreakers.keyboardType = UIKeyboardType.NumberPad
}



@IBAction func userTappedBackground(sender: AnyObject)
{
    view.endEditing(true)
}

override func shouldPerformSegueWithIdentifier(identifier: String!, sender: AnyObject!) -> Bool {
    if identifier == "segueTest" {

        if (APTeams.text!.isEmpty) {

            let alert = UIAlertView()
            alert.title = "No Text"
            alert.message = "Please Enter Text In The Box"
            alert.addButtonWithTitle("Ok")
            alert.show()

            return false
        }

        else {
            return true
        }
    }

    // by default, transition
    return true

}


    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

        if (segue.identifier == "segueTest"){

            var passs = segue.destinationViewController as! View3on3Results

                passs.AP1 = APTeams.text!
                passs.AP2 = APRounds.text!
                passs.AP3 = APBreakers.text!
        }


}
}

我尝试查看有关 SO 的其他问题，但解决方案都引发了错误。我认为这是由于 Swift 更新到 2.0。我可能是错的-对此很陌生。

Answer 1

我希望这可能是因为 AlertView。在 swift 2.0 中，UIAlertView 被 UIAlertController 取代:

let alertController: UIAlertController = UIAlertController(title: "Hello", message: "Are you sure?", preferredStyle: UIAlertControllerStyle.Alert)

let okAction = UIAlertAction(title: "Yes", style: UIAlertActionStyle.Default, handler: nil)

alertController.addAction(okAction)

presentViewController(alertController, animated: true, completion: nil)

使用上面的代码用 UIAlertViewController 替换你的 UIAlertView。

编辑:

同时使 IBOutlet 成为可选项:

@IBOutlet weak var APTeams: UITextField?
@IBOutlet weak var APRounds: UITextField?
@IBOutlet weak var APBreakers: UITextField?