Today I Learned

Study the docs. As an example, there are so many methods on Enumerable that you can leverage to eliminate temporary variables. Don’t spend all your time reading the docs, but every once and a while it’s good to review what’s already built in the standard library that you don’t need to re-invent.

If you’re looking up a record by anything other than the primary_key, don’t accept arbitrary arguments. Lazily looking up a record is great, but if you’re using something like

def destroy_do_dad(expecting_an_id_but_an_object_was_passed_in)
  DoDad.where(foreign_system_id: expecting_an_id_but_an_object_was_passed_in).destroy
end

you have a huge vulnerability. #to_param, will come into play, and you’re now potentially finding a completely arbitrary record and destroying it.