swift - Swift 3 协议(protocol)中的静态关键字

Question

我注意到 Swift protocols 中的某些函数具有 static 关键字。但是，当您实现该功能时，您必须删除 static 关键字以使编译器满意。

public static func <(lhs: Self, rhs: Self) -> Bool

static 在上下文中是什么意思，它的目的是什么？

Answer 1

来自 Xcode 8 beta 4 发行说明:

Operators can be defined within types or extensions thereof. For example:

struct Foo: Equatable {
    let value: Int
    static func ==(lhs: Foo, rhs: Foo) -> Bool {
        return lhs.value == rhs.value
    }
}

Such operators must be declared as static (or, within a class, class final), and have the same signature as their global counterparts. As part of this change, operator requirements declared in protocols must also be explicitly declared static:

protocol Equatable {
    static func ==(lhs: Self, rhs: Self) -> Bool
}