Swift :在整数的情况下切换 nil 值

Question

我在代码中的问题：

  if let x = UserDefaults.standard.object(forKey: "carT") as? String {
            carTpass.text = x
        }
        if let x2 = UserDefaults.standard.object(forKey: "carM") as? String {
            carMpass.text = x2
        }
        if let x3 = UserDefaults.standard.object(forKey: "carCom") as? String {
            carCompass.text = x3
        }
 @IBAction func calc(_ sender: UIButton) {
        let statusCode:Int = Int(carMpass.text!)!
        switch (carTpass.text ,carCompass.text, statusCode) {
        case ("BMW"?,"X"?,2008 ... 2010):
            result.text = "Yes"
        default:
            result.text = "No"
        }

现在我的问题是：

如果状态代码为nil，应用程序将崩溃，因为解开的整数，我该如何解决？

carTpass.text 、carCompass.text 和 carMpass.text 它们是来自另一个视图控制器 (tableView( 的数据

Answer 1

只需像在其他地方使用if let一样使用

@IBAction func calc(_ sender: UIButton) {
    if let text = carMpass.text, let statusCode = Int(text) {
        switch (carTpass.text ,carCompass.text, statusCode) {
        case ("BMW"?,"X"?,2008 ... 2010):
            result.text = "Yes"
        default:
            result.text = "No"
        }
    }
}

Answer 2

您也可以对范围应用可选的解包

let statusCode = carMpass.text.flatMap(Int.init)
switch (carTpass.text ,carCompass.text, statusCode) {
case ("BMW"?, "X"?, (2008 ... 2010)?):
    result.text = "Yes"
default:
    result.text = "No"
}