如何实现Swift的Comparable协议？ [英] How do I implement Swift's Comparable protocol?

问题描述

如何在Swift中使用Comparable协议？在声明中说，我必须实现三个操作<，< =和> =。我把所有的那些在类，但它不工作。还需要我有三个人吗？

How do I use the Comparable protocol in Swift? In the declaration it says I'd have to implement the three operations <, <= and >=. I put all those in the class but it doesn't work. Also do I need to have all three of them? Because it should be possible to deduce all of them from a single one.

推荐答案

Comparable协议扩展了Equatable协议 - >实现两者

The Comparable protocol extends the Equatable protocol -> implement both of them

在 Apple's Reference 是来自Apple的一个示例（在Comparable协议参考中），您可以看到您应该如何做：不要将操作实现放在类中，而是放在外部/全局范围。此外，您只需要从可比较的协议和 == 实现< code>从等于协议。

In Apple's Reference is an example from Apple (within the Comparable protocol reference) you can see how you should do it: Don't put the operation implementations within the class, but rather on the outside/global scope. Also you only have to implement the < operator from Comparable protocol and == from Equatable protocol.

正确的示例：

class Person : Comparable {
    let name : String

    init(name : String) {
        self.name = name
    }
}

func < (lhs: Person, rhs: Person) -> Bool {
    return lhs.name < rhs.name
}

func == (lhs: Person, rhs: Person) -> Bool {
    return lhs.name == rhs.name
}

let paul = Person(name: "Paul")
let otherPaul = Person(name: "Paul")
let ben = Person(name: "Ben")

paul > otherPaul  // false
paul <= ben       // false
paul == otherPaul // true

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