Rails: When a model? When a lib?

Question

I'm making a little message sending module. It'll handle queuing messages from a request to be picked up by a background worker to send email/SMS (or log appropriately for testing).

Question: is this a Model (under /app/models) or a lib (under /lib).

I'd like some religion on this.

Theory A: (My current theory) Unless you're subclassing ActionMailer::Base or ActiveRecord::Base, etc, your code should go into lib.

Theory B: (Theory I'm leaning towards) Things that are application-specific should be in model. Anything that could be of general use should be in lib.

Theory C: only "data models" should be in 'models'. ActionMailer subclasses break this rule, though.

As far as I know, either way it'll work fine, but I'm looking for any subtle functional or philosophical reasons for one vs. the other.

Thoughts?

Answer 1

Whether or not messages inherit from ActiveRecord or ActionMailer, you likely want a model for any objects that your views and controllers interact with. In your case, they will handle instances of the Message class -- you want a model for that.

As for the message sending module -- extracting out to a library is great if you plan to reuse the code elsewhere where you can just include the module in any class.

Since this is just a "little" message sending module, you might want to start in the model and eventually extract out to a separate module if it could be useful elsewhere or your model gets too messy.