Question about defining methods within class << self in an ActiveRecord model

[pdbradley (Philip Bradley)]

I’m not sure if this is appropriate but since Chad Pytel coauthored this book maybe I can ask here too.

I’m not clear about why you would define the methods referenced in this stack overflow post as class methods and not instance methods. Can anyone shed light?

What is the purpose of this example from the 'Rails antipatterns' book: class << self defining methods in an ActiveRecord class