Code for comment on 'How language features affect OO design'

main.dart

main() {
  new Dog().feed("some food");
}

abstract class Pet {
  void feed(String food);
  void pet();
}

class Dog = Pet with FeedableDog, PettableDog;
class Cat = Pet with FeedableCat, PettableCat;

mixin FeedableDog on Pet {
  void feed(String food) => print(food + "? For me?");
}

mixin FeedableCat on Pet {
  void feed(String food) => print(food + "? Of course.");
}

mixin PettableDog on Pet {
  void pet() => print("Yay!");
}

mixin PettableCat on Pet {
  void pet() => print("I'll allow it.");
}

// Of course, we could define interfaces `PettablePet`,
// `FeedablePet`, and add `implements PettablePet` etc.
// on the mixins. That would allow for more abstract code
// when each feature is accessed.