将枚举与Swift中的关联值进行比较

Question

For enums with associated values, Swift doesn't provide the equality operator. So I implemented one to be able to compare two enums:

enum ExampleEnum{
     case Case1
     case Case2(Int)
     case Case3(String)
     ...
}

func ==(lhs: ExampleEnum, rhs: ExampleEnum) -> Bool {

    switch(lhs, rhs){
    case (.Case1, .Case1): return true
    case let (.Case2(l), .Case2(r)): return l == r
    case let (.Case3(l), .Case3(r)): return l == r
    ...
    default: return false
    }
}

My problem is that I have a lot of such enums with a lot of cases so I need to write a lot of this comparison code (for every enum, for every case).

As you can see, this code always follows the same scheme, so there seems to be a more abstract way to implement the comparison behavior. Is there a way to solve this problem? For example with generics?

Answer 1

Currently there is no way of achieving this without writing out all the cases, we can hope that it'll be possible in a later version.

If you really have a lot of cases and you don't want to write them all out, you can write a small function that generates the code automatically for you (I've been doing this just recently for something that wasn't possible to refactor)

Answer 2

As of Swift 4.2 just add Equatable protocol conformance. It will be implemented automatically.

enum ExampleEquatableEnum: Equatable {
    case case1
    case case2(Int)
    case case3(String)
}

print("ExampleEquatableEnum.case2(2) == ExampleEquatableEnum.case2(2) is \(ExampleEquatableEnum.case2(2) == ExampleEquatableEnum.case2(2))")
print("ExampleEquatableEnum.case2(1) == ExampleEquatableEnum.case2(2) is \(ExampleEquatableEnum.case2(1) == ExampleEquatableEnum.case2(2))")

Ie default comparison takes associated values in account.