Question

I’m trying to create a class called Musician which inherits from my class Person and then adds an instrument attribute. I know my Musician class is wrong, but I just wanted to know what the correct format is in Ruby. Here is all of my code:

class Person
  attr_reader :first_name, :last_name, :age
  def initialize (first_name, last_name, age)
    @first_name = first_name
    @last_name = last_name
    @age = age
  end
end

p = Person.new("Earl", "Rubens-Watts", 2)
p.first_name
p.last_name
p.age


class Musician < Person
  attr_reader :instrument
  def initialize (instrument)
    @instrument = instrument
  end
end

m = Musician.new("George", "Harrison", 58, "guitar")
m.first_name + " " + m.last_name + ": " + m.age.to_s
m.instrument

Thanks for the help!

Answer 1

If you want first_name, last_name and age to be available in Musician then you must include them in the initializer and take advantage of super. Something like:

class Musician < Person
  attr_reader :instrument

  def initialize(first_name, last_name, age, instrument)
    super(first_name, last_name, age)
    @instrument = instrument
  end
end

super calls the method with the same name inside of the parent class.

UPDATE

I will drive the point home. You would also use super in this totally made up situation:

class GuitarPlayer < Person
  attr_reader :instrument

  def initialize(first_name, last_name, age)
    super(first_name, last_name, age)
    @instrument = 'guitar'
  end
end

We haven’t changed the arguments to initialize but we have extended the behavior.