Question

在我正在撰写的应用程序中，我有一个名为“User”的字符串，用于存储游戏的用户名。当在Swift文件中的任何其他位置打印时，字符串的值将打印我设置的值，作为可选项。

如果我尝试将此字符串用作操作表操作的标题，则该字符串将自动设置为nil，我可以将其视为操作的标题，并在我要求打印时打印该字符串（用户））。

如果有人能够解释为什么会发生这种情况，或者如何防止这种情况发生，那就太好了。我还在下面发布了我的Swift文件，谢谢。

import UIKit

class MainViewController: UIViewController {

@IBOutlet weak var segmentedControl: UISegmentedControl!
@IBOutlet weak var firstView: UIView!
@IBOutlet weak var secondView: UIView!

var user:String!
var playerTwo:String!
var playerThree:String!
var playerFour:String!
var playerFive:String!
var playerSix:String!

var userCards = [String]()

override func viewDidLoad() {
    super.viewDidLoad()

    firstView?.isHidden = false
    secondView?.isHidden = true

}

@IBAction func valueDidChange(_ sender: UISegmentedControl) {

    switch segmentedControl.selectedSegmentIndex {
    case 0:
        firstView.isHidden = false
        secondView.isHidden = true
    case 1:
        firstView.isHidden = true
        secondView.isHidden = false
    default:
        break;
    }
}

@IBAction func confirm(_ sender: UIButton) {

    let alertController = UIAlertController(title: "Action Sheet", message: "What would you like to do?", preferredStyle: .actionSheet)

    let userButton = UIAlertAction(title: user /* Here I have tried with putting both 'user', and "\(user)"*/, style: .default, handler: { (action) -> Void in
        print("User button tapped")
    })

    let  deleteButton = UIAlertAction(title: "Delete button test", style: .destructive, handler: { (action) -> Void in
        print("Delete button tapped")
    })

    let cancelButton = UIAlertAction(title: "Cancel", style: .cancel, handler: { (action) -> Void in
        print("Cancel button tapped")
    })


    alertController.addAction(userButton)
    alertController.addAction(deleteButton)
    alertController.addAction(cancelButton)

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

}
}

该值直接从另一个文件中的代码传递到上面的文件中：

覆盖func prepare（对于segue：UIStoryboardSegue，sender：Any？）{

    if segue.identifier == "showMainController" {

        let VC = segue.destination as! MainViewController

        VC.user = self.user

        if playerTwo != nil {

            VC.playerTwo = self.playerTwo

        }

        if playerThree != nil {

            VC.playerThree = self.playerThree

        }

        if playerFour != nil {

            VC.playerFour = self.playerFour

        }

        if playerFive != nil {

            VC.playerFive = self.playerFive

        }

        if playerSix != nil {

            VC.playerSix = self.playerSix

        }
    }
}

但是，该值通过多个视图控制器传递，最初在此处设置：

if (meTextField.text?.isEmpty)! == false {

        let p1 = meTextField.text!
        initialPlayersDict["player1"] = "\(p1)"

        if errLabelNotBlank {

            errorLabel.text = ""
            errLabelNotBlank = false

        }

    }

当用作行动表的标题时，为什么我的字符串变为零？

0 个答案: