swift - 无法匹配类型的值

Question

我刚开始使用 Swift 3，我正在将 Rails 项目转换为 swift(我学习时的副项目)

相当简单，我有一个正在转换的 Rails 语句，我在 Xcode 中收到许多红色错误:

let startingPoint: Int = 1
let firstRange: ClosedRange = (2...10)
let secondRange: ClosedRange = (11...20)

func calc(range: Float) -> Float {
  switch range {
    case startingPoint:
     return (range - startingPoint) * 1 // or 0.2
    case firstRange:
     return // code
    default:
     return //code
  }
}

calc 将有一个 Int 或 Float 值:10 或 10.50

错误是:

Expression pattern of type ClosedRange cannot match values of type Float

Binary operator - cannot be applied to operands of type Float and Int

我了解这些错误，但我不知道要搜索什么来更正错误。你能给我指出正确的方向吗？

Answer 1

Swift 是强类型的。每当你使用变量或将某些东西作为函数参数传递时，Swift 会检查它的类型是否正确。您不能将字符串传递给需要整数等的函数。Swift 在编译时进行此检查(因为它是静态类型的)。​​

要遵守该规则，请尝试将您的代码更改为:

let startingPoint: Float = 1
let firstRange: ClosedRange<Float> = (2...10)
let secondRange: ClosedRange<Float> = (11...20)

func calc(range: Float) -> Float {
    switch range {
    case startingPoint:
        return (range - startingPoint) * 1 // or 0.2
    case firstRange:
    return 1.0 // 1.0 is just an example, but you have to return Float since that is defined in the method
    default:
        return 0.0 // 0.0 is just an example, put whatever you need here
    }
}