ruby-on-rails - Rails 5, Concerns - can they reference a database table?

Question

I'm trying to learn about concerns.

Most of the blog posts and examples I can find discuss them in the context of moving class methods defined in a model to a common repository. I understand that part.

I don't understand whether concerns can be used to reduce the setup for associated models. For example, I have a user model and an organisation model. Each of user and organisation will have an address.

If address is a model, it will be polymorphic and belong to addressable. Then user and organisation will each have one address.

I am trying to understand whether I can make address a concern and then include it in my user and organisation models. If so, can I still have a table in the database called address? It's not clear to me whether I can have the db table if I don't have a model called address (which I wouldn't need if I used concerns subfolder in the models folder to define address).

Answer 1

Yes, you can certainly do this, and it's pretty common. You'll still need an Address model and addresses table in the database.

It would look something like this:

# your user model (backed by users table)
class User < ApplicationRecord
   include Addressable
end

# your organisation model (backed by organisations table)
class Organisation < ApplicationRecord
  include Addressable
end

# your address model (backed by addresses table)
class Address < ApplicationRecord
  belongs_to :addressable, polymorphic: true, touch: true
end

# the concern to DRY up shared relation that both user adn organisation have
module Addressable
  extend ActiveSupport::Concern

  included do
    has_one :address, as: :addressable, dependent: :destroy
  end
end