Course of Raku / Objects, I/O, and exceptions / Classes and objects / Roles / Exercises / A dancing robot

Solution: A dancing robot

Here is a possible solution to the task.

Code

role Dancing {
    method dance {
        'spinning around';
    }
}

class Robot {
    method speak {
        'beep';
    }
}

my $plain   = Robot.new;
my $dancing = Robot.new but Dancing;

say $plain.speak;
say $dancing.speak;
say $dancing.dance;

🦋 You can find the source code in the file dancing-robot.raku.

Output

beep
beep
spinning around

Comments

1. Unlike the earlier examples, Dancing does not replace an existing method — it brings a brand-new dance method that Robot knows nothing about.

2. Robot.new but Dancing mixes the role into a single object at run time, so $dancing can both speak (from the class) and dance (from the role). The plain $plain only ever learnt speak.

3. The extra ability belongs to that one object, not to the Robot class. Calling $plain.dance would be an error, because $plain never received the role.

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