own.rb

class Foo
  attr_accessor :bar
  visible_owner :bar
end

class Chicken
  def initialize
    @foo = Foo.new
    
    @foo.bar = 1234
  end
end

begin
  foo = Foo.new
  foo.bar = 1234
  
  chicken = Chicken.new
  chicken.foo.bar = 1234 # error
end