Question

我在玩RoShambo的应用程序方面取得了一些进展，但我对一件特别的事情感到难过。在一个ViewController中，我已经建立了该类的两个属性。我希望它们是整数，因为我稍后在类中使用带有整数的switch语句。但是，当我使用整数说：

时，我收到错误

"Class 'ResultsViewController' has no initializers"
"stored property 'your play' without initial value prevents synthesized initializers"

现在，如果我创建了我的存储属性选项，那些错误就会消失，但是我的switch语句会出现错误，因为它使用的是整数，而不是选项。

所以我有两个问题：1）在下面的switch语句中，我将如何使用＆＃34; Int？＆＃34;类型的值？在switch语句中？

2）如果我的可选值为零，我怎么能结束程序而不执行switch语句，因为进行比较是没有意义的呢？

import Foundation
import UIKit

class ResultsViewController: UIViewController {

// MARK: Properties

var opponentPlay: Int?
var yourPlay: Int?

//Mark: Outlets

@IBOutlet weak var MatchResult: UILabel!
@IBOutlet weak var PlayAgainButton: UIButton!


//Mark: Life Cycle

     override func viewWillAppear(_ animated: Bool){
        //unwrap optional properties
        if let opponentPlay = opponentPlay {
            print("good play")
        } else {
            print("opponentPlay is nil")

        }

        if let yourPlay = yourPlay {
            print("good play")
        } else {
            print("opponentPlay is nil")
        }


    switch (opponentPlay, yourPlay) {
        case (1, 1), (1, 1), (2, 2), (2, 2), (3, 3), (3, 3):
            self.MatchResult.text = "You Tie!"
        case (1, 2):
            self.MatchResult.text = "You Win!"
        case (2, 1):
            self.MatchResult.text = "You Lose!"
        case (1, 3):
            self.MatchResult.text = "You Lose!"
        case (3, 1):
            self.MatchResult.text = "You Win!"
        case (2, 3):
            self.MatchResult.text = "You Win!"
        case (3, 2):
            self.MatchResult.text = "You Lose!"
        default:
            break
    }

Answer 1

您可以使用?打开包装。您还可以添加where条款，如果您不想列举每个排列，无论您是赢还是丢失：

switch (opponentPlay, yourPlay) {
case (nil, nil):
    print("both nil")
case (nil, _):
    print("opponent score nil")
case (_, nil):
    print("yours is nil")
case (let opponent?, let yours?) where opponent == yours:
    matchResult.text = "tie"
case (let opponent?, let yours?) where opponent > yours:
    matchResult.text = "you win"
case (let opponent?, let yours?) where opponent < yours:
    matchResult.text = "you lose"
default:
    fatalError("you should never get here")
}

Answer 2

我执行的代码与您的代码类似，但不会产生错误。我真的不知道switch是否接受选项，但我认为在这种情况下它也没有必要。我希望它对你有用。

var opponentPlay: Int?
var yourPlay: Int?
var matchResult = ""

func play (){
  if let opponentPlay = opponentPlay , let yourplay = yourPlay {
    switch (opponentPlay,yourplay) {
    case (1,1):
        matchResult = "You tie"
    default:
        break
    }
  }
}

如何在Switch语句中使用Optional Ints

2 个答案: