Using class << self, when to use classes or modules?

class, module, ruby, self

Solution

The `class<<self` seems to be a red herring, as the only difference here is a class versus a module. Perhaps you're asking "I want to create an object that I do not intend to instantiate, but which exists only as a namespace for some methods (and possibly as a singleton with its own, global, state)."

If this is the case, both will function equally well. If there is any chance that you might want to create a derivative (another object inheriting the same methods) then you should use a class as it slightly is easier to write:

class Variation < Helper

instead of

module Helper
  module OwnMethods
    # Put methods here instead of class << self
  end
  extend OwnMethods
end

module Variation
  extend Helper::OwnMethods

However, for just namespacing I would generally use a module over a class, as a class implies that instantiation will occur.

Problem

Is there a difference in usage between ``` class Helper class << self # ... end end ``` and ``` module Helper class << self # ... end end ``` When would you use one over the other?

Original source