Swift 2 -“if”模式匹配

Recently I've saw the WWDC 2015 keynote from Apple. I also looked at some documentation but I can't find a "pattern matching in if" section, how it was written on one of the slides which they have shown. (68min 00sec video from Apple Events)

最近我看到了苹果2015年全球开发者大会的主题演讲。我还查看了一些文档，但是我找不到if部分中的“模式匹配”部分，这部分是如何写在他们展示的其中一张幻灯片上的。(来自苹果事件的68min视频)

Do you know what's this refers to? Or the syntax?

你知道这指的是什么吗?还是语法?

1 个解决方案

#1

All it really means is that if statements now support pattern matching like switch statements already have. For example, the following is now a valid way of using if/else if/else statements to "switch" over the cases of an enum.

它真正的意思是if语句现在支持模式匹配，比如switch语句。例如，下面是使用if/else if/else语句在枚举的情况下“切换”的有效方法。

enum TestEnum {
    case One
    case Two
    case Three
}

let state = TestEnum.Three

if case .One = state {
    print("1")
} else if case .Two = state {
    print("2")
} else {
    print("3")
}

And the following is now an acceptable way of checking if someInteger is within a given range.

下面是一种可以接受的检查某个整数是否在给定范围内的方法。

let someInteger = 42
if case 0...100 = someInteger {
    // ...
}

Here are a couple more examples using the optional pattern from The Swift Programming Language

下面是使用Swift编程语言中的可选模式的几个示例

let someOptional: Int? = 42
// Match using an enumeration case pattern
if case .Some(let x) = someOptional {
    print(x)
}

// Match using an optional pattern
if case let x? = someOptional {
    print(x)
}

#1