ruby.rb

class A
  def initialize(owner)
    @owner = owner
  end

  def owner_name
    @owner.class.name.split("::").last
  end

  def do_stuff
    puts owner_name
  end
end

class B
  def initialize
    @a = A.new(self)
  end

  def do_stuff
    @a.do_stuff
  end
end

b = B.new

b.do_stuff