与阵列匹配的快速切换模式

Curious if there is a way to do the following in Swift.

好奇是否有一种方法可以快速地做到以下几点。

let foo = [1, 2, 3]
let bar = [4, 5, 6]

let value = 5

switch value {
case in foo
    print("5 is in foo")
case in bar
    print("5 is in bar")
default:
    break
}

I understand there are other ways I could make this contrived example work such as case 4, 5, 6: or not using a switch and instead using bar.contains(value) but I'm looking for a solution specifically involving switch pattern matching to an array. Thanks!

我知道还有其他方法可以使这个设计的示例工作，比如情形4、5、6:或者不使用开关，而是使用bar.contains(value)，但是我正在寻找一个解决方案，具体涉及到与数组匹配的开关模式。谢谢!

2 个解决方案

#1

You could define a custom pattern matching operator ~= which takes an array as the "pattern" and a value:

您可以定义一个自定义模式匹配操作符~=它将一个数组作为“模式”和一个值:

func ~=<T : Equatable>(array: [T], value: T) -> Bool {
    return array.contains(value)
}

let foo = [1, 2, 3]
let bar = [4, 5, 6]

let value = 5

switch value {
case foo:
    print("\(value) is in foo")
case bar:
    print("\(value) is in bar")
default:
    break
}

Similar operators exist already e.g. for intervals:

类似的运算符已经存在，例如间隔:

public func ~=<I : IntervalType>(pattern: I, value: I.Bound) -> Bool

#2

How about:

如何:

let foo = [1, 2, 3]
let bar = [4, 5, 6]

let value = 5

switch value {
case _ where foo.contains(value):
    print("\(value) is in foo")
case _ where bar.contains(value):
    print("\(value) is in bar")
default:
    print("\(value) is not in foo or bar")
}

#1