Inheritance

Derive a class with is, and override methods in the subclass.

A class inherits from another with is. The subclass gains the parent's attributes and methods, and may override any method by declaring one of the same name.

Subclass and override #

class Animal {
    method speak { "..." }
}
class Dog is Animal {
    method speak { "Woof" }
}
say Dog.new.speak;

Woof

Dog inherits from Animal but replaces speak, so Dog.new.speak is Woof.

Calling the overridden method #

An override can still reach the method it replaced. callsame runs the next candidate up the inheritance chain — the parent's version — so a subclass can extend behaviour rather than discard it.

class Animal { method describe { "an animal" } }
class Dog is Animal {
    method describe { callsame() ~ " that barks" }
}
say Dog.new.describe;

an animal that barks

Notes #

• callsame is one of a small family (nextsame, callwith, nextwith, samewith) for invoking the next candidate — see Re-dispatch. You can also name the parent explicitly with self.Animal::describe.
• Raku supports multiple inheritance (is A is B), but composing roles is usually the better tool for sharing behaviour — see Roles.
• Every class ultimately inherits from Mu (via Any), which is where universal methods like .WHAT and .defined come from.