Is there a way to test an OptionSet with a switch statement?

Question

Defining a simple OptionSet:

public struct TestSet : OptionSet, Hashable
{
    public let rawValue: Int
    public init(rawValue:Int){ self.rawValue = rawValue}
         


        

Answer 1

You can't do this directly because switch is using Equatable and, I think, is using SetAlgebra.

However, you can wrap the OptionSet with something like:

public struct TestSetEquatable<T: OptionSet>: Equatable {

    let optionSet: T

    public static func == (lhs: Self, rhs: Self) -> Bool {

        return lhs.optionSet.isSuperset(of: rhs.optionSet)
    }
}

Which lets you do:

let ostest : TestSet = [.A, .C]

switch TestSetEquatable(optionSet: ostest) {

  case TestSetEquatable(optionSet: [.A, .B]):
   print("-AB")
   fallthrough

 case TestSetEquatable(optionSet: [.A, .C]):
   print("-AC")
   fallthrough

 case TestSetEquatable(optionSet: [.A]):
   print("-A")
   fallthrough

   default:
     print("-")
}

This prints:

-AC
-A
- // from the fall through to default

Opinion: I'm not inclined to do use this code myself but if I had to, this is what I would do.