〜= Swift中的运算符 [英] ~= operator in Swift

问题描述

我最近从Apple下载了高级NSOperations 示例应用，发现此代码...

I recently downloaded the Advanced NSOperations sample app from Apple and found this code...

// Operators to use in the switch statement.
private func ~=(lhs: (String, Int, String?), rhs: (String, Int, String?)) -> Bool {
    return lhs.0 ~= rhs.0 && lhs.1 ~= rhs.1 && lhs.2 == rhs.2
}

private func ~=(lhs: (String, OperationErrorCode, String), rhs: (String, Int, String?)) -> Bool {
    return lhs.0 ~= rhs.0 && lhs.1.rawValue ~= rhs.1 && lhs.2 == rhs.2
}

似乎使用〜= 运算符字符串和 Ints 但我从未见过它之前。

It seems to use the ~= operator against Strings and Ints but I've never seen it before.

这是什么？

推荐答案

这是一个运算符用于 case 语句中的模式匹配。

It is an operator used for pattern matching in a case statement.

您可以在这里了解如何使用和利用它来提供您自己的实现：

You can take a look here to know how you can use and leverage it providing your own implementation:

• http://oleb.net/blog/2015 / 09 / swift-pattern-matching /


• http://austinzheng.com/2014/12/17/custom-pattern-matching/

• http://oleb.net/blog/2015/09/swift-pattern-matching/
• http://austinzheng.com/2014/12/17/custom-pattern-matching/

这是一个定义自定义并使用它的简单示例：

Here is a simple example of defining a custom one and using it:

struct Person {
    let name : String
}

// Function that should return true if value matches against pattern
func ~=(pattern: String, value: Person) -> Bool {
    return value.name == pattern
}

let p = Person(name: "Alessandro")

switch p {
// This will call our custom ~= implementation, all done through type inference
case "Alessandro":
    print("Hey it's me!")
default:
    print("Not me")
}
// Output: "Hey it's me!"

if case "Alessandro" = p {
    print("It's still me!")
}
// Output: "It's still me!"

这篇关于〜= Swift中的运算符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！