ios - 如何在 Switch 语句中使用可选整数

Question

我在玩 RoShambo 的应用程序上取得了一些进展，但我对一件事感到困惑。在一个 ViewController 中，我建立了该类的两个属性。我希望它们是整数，因为稍后我会在带有整数的类中使用 switch 语句。但是，当我使用整数时出现错误:

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

现在，如果我将存储的属性设置为可选值，这些错误就会消失，但随后我的 switch 语句会出错，因为它使用整数，而不是可选值。

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

2) 如果我的可选值为 nil，我怎么能结束程序而不执行 switch 语句，因为执行比较没有意义？

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

你可以用 ? 解包。如果你不想枚举每个排列，你也可以添加 where 子句，无论你赢了还是输了:

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")
}