Shows how Ruby mixins work together with `super`

ruby-mixins.rb

##
## with raw object
##

# create a new object
o = Object.new

# define methods on the object (precisely, the object's singleton)
class << o
  def hello(thing)
    puts "hello #{thing}"
  end
end

module Yeller
  def hello(thing)
    super thing.upcase
  end
end

module Queryer
  def hello(thing)
    super "#{thing}?"
  end
end

# apply the Yeller mixin to the object
o.extend Yeller

# apply the Queryer mixin to the object
o.extend Queryer

o.hello "world" #=> hello WORLD?


##
## with classes
##

class Person
  include Yeller
  include Queryer

  def hello(thing)
    puts "hello #{thing}"
  end
end

Person.new.hello "world" #=> hello WORLD?

This is printing "hello world" for me for both o.hello and Person.new.hello. The only way this works for me is if I subclass Person and include the modules on the subclass:

class Person

  def hello(thing)
    puts "hello #{thing}"
  end
end

class Owner < Person
  include Yeller
  include Queryer

end

Person.new.hello "world" #=> hello world
Owner.new.hello "world" #=> hello WORLD?