“Who cares? Let’s just go with the style-guide” — to which my response is that caring about the details is in the heart of much of our doings. Yes, this is not a major issue; def self.method is not even a code smell. Actually, that whole debate is on the verge of being incidental. Yet the learning process and the gained knowledge involved in understanding each choice is alone worth the discussion. Furthermore, I believe that the class << self notation echoes a better, more stable understanding of Ruby and Object Orientation in Ruby. Lastly, remember that style-guides may change or be altered (carefully, though!).

Similarly to fashion, code style reflects our credo as developers, our values and philosophy.

Yet, it certainly is important to make the proper choices when picking up style. Similarly to fashion, code style reflects our credo as developers, our values and philosophy. In order to make an informed decision, it’s mandatory to understand the issue at stake well. We all have defined class methods many times, but do we really know how do they work?

However, know when to be inconsistent -- sometimes style guide recommendations just aren't applicable.