I am currently working through the Gregory Brown Ruby Best Practices book. Early on, he is talking about refactoring some functionality from helper methods on a related class, to some methods on module, then had the module extend self.

Hadn't seen that before, after a quick google, found out that extend self on a module lets methods defined on the module see each other, which makes sense.

Now, my question is when would you do something like this

module StyleParser
  extend self

  def process(text)
    ...
  end

  def style_tag?(text)
    ...
  end
end

and then refer to it in tests with

@parser = Prawn::Document::Text::StyleParser

as opposed to just using a class with some class methods on it? is it so that you can use it as a mixin? or are there other reasons I'm not seeing?