how to write an equal method for private enum in Swift

Question

I'm new to Swift and was trying to write a private enum that conforms Equatable. Here is a simplified representation of my code:

class Baz {

    /* Other members in class Baz */

    private enum Test: Equatable {
        case Foo
        case Bar
    }

    private func == (lhs: Test, rhs: Test) -> Bool {
        //comparison
    }
}

On the line of the "==" method, the compiler is complaining "Operators are only allowed at global scope". And when I change enum Test and "==" method to public then move the "==" out of the class, then the errors go away.

My question is what is the correct way to implement the "==" method for a private enum?

Any help is appreciated.

========

Edit:

Thanks all for helping me out. I didn't specify that my private enum and function above are in a class.. (Code is updated)

Answer 1

While perhaps not immediately useful for you, it's worth noting that as of beta 5, in Swift 3 you can make this a static func within the type. See the Xcode 8 Beta Release Notes, which says

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.

This works with enum types, too. Thus:

private enum Test: Equatable {
    case foo
    case bar

    static func ==(lhs: Test, rhs: Test) -> Bool {
        // your test here
    }
}

And this even works when this Test is implemented within another type.