小于或大于 Swift switch 语句 [英] Lesser than or greater than in Swift switch statement

问题描述

我熟悉 Swift 中的 switch 语句，但想知道如何用 switch 替换这段代码:

I am familiar with switch statements in Swift, but wondering how to replace this piece of code with a switch:

if someVar < 0 {
    // do something
} else if someVar == 0 {
    // do something else
} else if someVar > 0 {
    // etc
}

推荐答案

这是一种方法.假设 someVar 是 Int 或其他 Comparable，您可以选择将操作数分配给新变量.这使您可以使用 where 关键字以任意方式确定其范围:

Here's one approach. Assuming someVar is an Int or other Comparable, you can optionally assign the operand to a new variable. This lets you scope it however you want using the where keyword:

var someVar = 3

switch someVar {
case let x where x < 0:
    print("x is \(x)")
case let x where x == 0:
    print("x is \(x)")
case let x where x > 0:
    print("x is \(x)")
default:
    print("this is impossible")
}

这可以简化一点:

switch someVar {
case _ where someVar < 0:
    print("someVar is \(someVar)")
case 0:
    print("someVar is 0")
case _ where someVar > 0:
    print("someVar is \(someVar)")
default:
    print("this is impossible")
}

你也可以完全避免 where 关键字与范围匹配:

You can also avoid the where keyword entirely with range matching:

switch someVar {
case Int.min..<0:
    print("someVar is \(someVar)")
case 0:
    print("someVar is 0")
default:
    print("someVar is \(someVar)")
}

这篇关于小于或大于 Swift switch 语句的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！