协议扩展中的 .sort 不起作用 [英] .sort in protocol extension is not working

问题描述

我有一个协议和一个协议扩展，我想在协议扩展中实现一个函数，用自定义对象对协议定义的数组进行排序，但它不起作用.

I have a protocol as well as a protocol extension and I'd like to implement a function in the protocol extension to sort an array defined by the protocol with custom objects, but it's not working.

protocol MyProtocol {
    var myArray: [MyObject] { get set }
}

extension MyProtocol {
    func sortArrayByCreationTime() {
        myArray.sort {
            $0.created > $1.created
        }
    }
}

Xcode 告诉我sort"已重命名为sorted(by:)"，但如果我使用它，则会创建一个新数组，但我需要对旧数组进行排序，而不是新数组.

Xcode is telling me that 'sort' has been renamed to 'sorted(by:)', but if im using this a new array gets created, but I need the old array to be sorted, not a new one.

我做错了什么?

推荐答案

这是一个误导性错误 - 问题是您需要将 sortArrayByCreationTime() 方法标记为 mutating 为了告诉编译器它正在改变一个属性(因为协议可以被值和引用类型采用):

It's a misleading error – the problem is that you need to mark your sortArrayByCreationTime() method as mutating in order to tell the compiler that it's mutating a property (as protocols can be adopted by both value and reference types):

extension MyProtocol {
    mutating func sortArrayByCreationTime() {
        myArray.sort {
            $0.created > $1.created
        }
    }
}

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