我如何测试枚举案例与 Swift 4 中关联值的等效性

Question

我想测试几个枚举类型变量的等价性，像这样：

enum AnEnumeration {
  case aSimpleCase
  case anotherSimpleCase
  case aMoreComplexCase(String)
}

let a1 = AnEnumeration.aSimpleCase
let b1 = AnEnumeration.aSimpleCase
a1 == b1 // Should be true.

let a2 = AnEnumeration.aSimpleCase
let b2 = AnEnumeration.anotherSimpleCase
a2 == b2 // Should be false.

let a3 = AnEnumeration.aMoreComplexCase("Hello")
let b3 = AnEnumeration.aMoreComplexCase("Hello")
a3 == b3 // Should be true.

let a4 = AnEnumeration.aMoreComplexCase("Hello")
let b4 = AnEnumeration.aMoreComplexCase("World")
a3 == b3 // Should be false.

遗憾的是，这些都会产生这样的错误：

error: MyPlayground.playground:7:4: error: binary operator '==' cannot be applied to two 'AnEnumeration' operands
a1 == b1 // Should be true.
~~ ^  ~~

MyPlayground.playground:7:4: note: binary operator '==' cannot be synthesized for enums with associated values
a1 == b1 // Should be true.
~~ ^  ~~

翻译：如果您的枚举使用关联值，则无法测试它的等效性。

注意：如果删除 .aMoreComplexCase（和相应的测试），则代码将按预期工作。

过去人们似乎决定使用运算符重载来解决这个问题：How to test equality of Swift enums with associated values。但是现在有了Swift4，不知道有没有更好的办法呢？或者是否有更改使链接的解决方案无效？

谢谢！

Answer 1

Swift提案

SE-0185 Synthesizing Equatable and Hashable conformance

已在 Swift 4.1 (Xcode 9.3):

中被接受和实施

... synthesize conformance to Equatable/Hashable if all of its members are Equatable/Hashable.

因此足以

... opt-in to automatic synthesis by declaring their type as Equatable or Hashable without implementing any of their requirements.

在您的示例中 – 因为 String 是 Equatable – 声明

就足够了

enum AnEnumeration: Equatable {
  case aSimpleCase
  case anotherSimpleCase
  case aMoreComplexCase(String)
}

编译器会合成一个合适的==运算符。

我如何测试枚举案例与 Swift 4 中关联值的等效性

How may I test the equivalency of enumeration cases with associated values in Swift 4

enums

equality

operators

swift

swift4