Swift protocol as parameter for both class and struct.

protocol-as-parameter.swift

protocol Named: class {
    var name: String { get set }
}

class Person: Named {
    var name: String

    init(name: String) {
        self.name = name
    }
}

struct Pet: Named {
    var name: String
}

func changeName<T: Named>(inout named: T, toName newName: String) {
    named.name = newName
}

var nick = Person(name: "nick")
changeName(nick, "NICK")
println(nick.name) // "NICK"

var maru = Pet(name: "Maru")
changeName(maru, "Hana")
println(maru.name) // "Hana"