Can I simulate traits/mixins in Swift?

Question

Does Swift have a way of mixing in traits, a la Scala? The section of the Swift book on using extensions to add protocols to existing classes comes tantalizingly close. However,

Answer 1

I don't know Scala, but from what you're telling me it is possible to simultaneously create a protocol and an extension that extends a type to add "pseudo-trait" behavior.

For example:

protocol IsGreaterThan
{
    func isGreaterThan(other:Int) -> Bool
    func isNotGreaterThan(other:Int) -> Bool
}

extension Int : IsGreaterThan
{
    func isGreaterThan(other:Int) -> Bool
    {
        return self > other
    }

    func isNotGreaterThan(other:Int) -> Bool
    {
        return !isGreaterThan(other)
    }
}

The real hamstring is how generics are somewhat limited for now. I think they will improve a lot in the coming revisions of Swift.