Swift protocol arrays

Hi

I have some struct objects that are heterogeneous like this

    struct Cat: Hashable {
       let name: String
       let catId: Int
    }
    struct SubCat: Hashable {
       let name: String
       let catId: Int
       let parentCatId: Int
    }

Now I have a tableView that needs to show either Cat or SubCat. My first choice was to extend both classes with a protocol :

  protocol Selectable {
        func asString() -> String
    }

and my struct became :

    struct Cat: Hashable, Selectable {
       let name: String
       let catId: Int
       func asString() -> {
          return self.name
      }
    }
    struct SubCat: Hashable, Selectable {
       let name: String
       let catId: Int
       let parentCatId: Int
       func asString() -> {
          return self.name
      }
    }

It worked so far.

I declared a [Selectable] object in my TableViewController, used asString() to populate my cells. Compiled like a charm.

But here's the thing. I've got a CatModel class and a SubCatModel class, each returning an array of each structs [Cats] and [SubCats]

When I try to assign the [Cat] array to the [Selectable] array, it does not compile. If I changed the return type of my [Cat] array to [Selectable], it does not compile.

Can anyone help me with this? I guess I'm missing something here.

Thanks.