Here’s a list of things that have been annoying, or at least a bit frustrating using Ohm, the Redis ORM, in a Rails app. Beware to those who assume Ohm is ActiveRecord in new clothes. It is, but it’s not:

CRUD

Don’t make the mistake of treating your Ohm objects like AR:

ActiveRecord	Ohm
destroy | delete`
self.find(id)	self[id]
update_attributes	update
create	create

Also note that Ohm’s update_attributes behaves differently from Rails` – it doesn’t persist the updates to DB. That owned me for the good part of the day.

Callbacks

Thankfully, these are ActiveRecord-like with the addition of ohm/contrib.

Associations

ActiveRecord	Ohm
has_a or belongs_to	reference
has_many	collection

Read this article if you’re considering creating associations from AR objects to Ohm objects and the other way ‘round.