在Swift中将输入字段字符串转换为Int

Question

所以我非常擅长制作APP广告Swift,我试图在文本字段中做一些非常简单的输入,取值,然后将它们用作Int进行一些计算.

但是'var distance'的某些方法是行不通的

        var handicapTal:Int
        var MagicNumber:Int
        var handicap = inputHCP.text.toInt()
        var distance = inputDistance.text.toInt()

        if (handicap >= 0 && handicap <= 20)
        {
            handicapTal = 30
        }
        else if(handicap > 20 && handicap <= 40){
            handicapTal = 10
        }

        MagicNumber = distance - handicapTal

它是导致错误的最后一行代码.它说致命错误:无法解开Optional.None

Answer 1

在你的例子中,距离是一个Int？也称为可选的Int..toInt()返回Int？因为从String到Int的转换可能失败.请参阅以下示例:

Welcome to Swift!  Type :help for assistance.
  1> let a = "12"
a: String = "12"
  2> let b = a.toInt()
b: Int? = 12
  3> let c = "Hello"
c: String = "Hello"
  4> let d = c.toInt()
d: Int? = nil
  5> if let e = a.toInt() { println("e = \(e)") }
e = 12
  6> if let f = c.toInt() { println("Huh?") }
  7>