Swift, Equatable 协议错误? [英] Swift, Equatable protocol bug?

问题描述

我正在 Swift 中构建一个非常简单的结构，其中包含一个可选值数组.此结构必须符合 Equatable 协议.这是代码:

I am building a very simple structure in Swift that contains an array of optional values. This struct must conform to the Equatable protocol. This is the code:

struct MyTable: Equatable {
    var values: [Int?] = Array(count: 64, repeatedValue: nil)
}

func == (lhs: MyTable, rhs: MyTable) -> Bool {
    return lhs.values == rhs.values
}

很简单.我没有看到任何错误，但编译器给出了错误:'[Int?]' 不能转换为 'MyTable'".我在做蠢事吗?或者这是编译器的错误?谢谢！

Quite simple. I see no mistakes, but the compiler gives error: "'[Int?]' is not convertible to 'MyTable'". Am I doing something stupid? or is this a compiler's bug? Thanks!

(使用 Xcode6-Beta5)

(Using Xcode6-Beta5)

推荐答案

不工作的原因是没有为具有可选元素的数组定义==运算符，仅用于非可选元素元素:

The reason why it does not work is there is no == operator defined for arrays with optional elements, only for non-optional elements:

/// Returns true if these arrays contain the same elements.
func ==<T : Equatable>(lhs: [T], rhs: [T]) -> Bool

您可以提供自己的:

func ==<T : Equatable>(lhs: [T?], rhs: [T?]) -> Bool {
    if lhs.count != rhs.count {
        return false
    }

    for index in 0..<lhs.count {
        if lhs[index] != rhs[index] {
            return false
        }
    }

    return true
}

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