Adopt.swift

class GermanShephard: Barker, DrugSniffer {
}

class BelgianMalinois: Barker, Swimmer, DrugSniffer {
}

class Poodle: Barker, Swimmer {
}

let belgian = BelgianMalinois()
belgian.bark() // prints "Bark!"
belgian.swim() // prints "Splash!"
belgian.sniffDrugs() // prints "I found drugs!"