Course of Raku / Objects, I/O, and exceptions / Classes and objects / Inheritance

Overriding methods

A child class can provide its own version of an inherited method. This is called overriding. When the method is called on an object of the child class, the child’s version runs instead of the parent’s.

class Animal {
    has $.name;
    method speak {
        'some sound';
    }
    method intro {
        "$.name says " ~ self.speak;
    }
}

class Dog is Animal {
    method speak {
        'Woof';
    }
}

class Cat is Animal {
    method speak {
        'Meow';
    }
}

Dog and Cat each override speak. The intro method, inherited unchanged from Animal, calls self.speak — and that call uses whichever speak belongs to the actual object:

say Dog.new(name => 'Rex').intro; # Rex says Woof
say Cat.new(name => 'Tom').intro; # Tom says Meow

So the same inherited intro produces different results, because each object brings its own speak. This is one of the central ideas of object-oriented programming: shared code that adapts to the specific kind of object it works on.

Course navigation

← Inheritance   |   Quiz — Inheritance →

💪 Or jump directly to the exercises in this section.