Question

I’m using ActiveSupport::Concern and I know there are a few approaches to organizing these into a /app/model/concern folder for say generic concerns but if I wanted to tie a concern to a specific model I have see a few approaches and would like to see some pros and cons

class Alert < ActiveRecord::Base
   include Shareable

concerns in the /app/models/alert folder

class Alert
   module Shareable
      extends ActiveSupport::Concern

or

module Alert::Shareable
   extends ActiveSupport::Concern

or

module Alert
   module Shareable
      extends ActiveSupport::Concern

Not really sure if there is a best way to do this or if I should use only modules or class module. I know it is trivial and they all seem to work but organizationally wasn’t sure if there is a best approach. Thanks!

Answer 1

If your model is Alert, you definitely don’t want module Alert (#3). #1 and #2 are basically the same, but more often you see the #2 style.

Let me explain a little further.

The module X::Y style will only work if X has already been defined. It’s saying “create this module Y under X and I don’t care if X is a class or module, just do it.

For #3, since Alert is already defined as a class, you’ll get this error: TypeError: Alert is not a module.

Let me know if you need more clarification.