mixins_and_scope_example.rb

module B
  def bee
    p cee
  end
end

module C
  def cee
    'hi'
  end
end

class A
  include B
  include C

  def hay
    bee
  end
end

a = A.new
a.hay # self is a, and all mixed-in methods are visible to a (in a's scope)