I used to prefer class << self because it is less repetition. Then I discovered this led to crashes in the GC in early ruby 2.x, so I switched for a while to c

I used to prefer class << self because it is less repetition. Then I discovered this led to crashes in the GC in early ruby 2.x, so I switched for a while to class self.method. Now I write an inner module ClassMethods and use extend at class scope. This I think makes it clearer that we are dealing with two distinct classes, the class and its metaclass (which is a factory).