Simple configurable extension to a class

configurable.rb

# Animals share some behaviour but each kind needs to be configured properly

# I used it to configure sidekiq workers that share sending metrics, logging,
# or error handling, but some of them don't send metrics for example
# and they need to be configured.

class Animal
  def say_hi
    puts(greeting_prefix + config.name + hobby_prefix + config.hobby)
  end

  private

  class Config
    attr_accessor :name, :hobby
  end

  class << self
    attr_accessor :config

    def configure
      yield(config)
    end

    def config
      @config ||= Config.new
    end
  end

  def config
    self.class.config
  end

  def hobby_prefix
    ' and I like '
  end
end

class Dog < Animal
  configure do |c|
    c.name = 'Scooby'
    c.hobby = 'diving'
  end

  def greeting_prefix
    'Woof woof, my name is '
  end
end

class Cat < Animal
  configure do |c|
    c.name = 'Suzy'
    c.hobby = 'walking'
  end

  def greeting_prefix
    'Miau miau, my name is '
  end
end

Dog.new.say_hi
Cat.new.say_hi

# Woof woof, my name is Scooby and I like diving
# Miau miau, my name is Suzy and I like walking