I saw the question of “How can I prevent a class from being reopened again in Ruby?” pop up on the Ruby mailing list. While this is somewhat against the nature of ruby, it can be accomplished:

{% codeblock lang:ruby %} class Foo def Foo.method_added(name) raise “This class is closed for modification” end end

class Foo def testing p “test” end end {% endcodeblock %}

This will raise an exception anytime someone tries to reopen the class.