Polymorphic association with abstract class in rails

Question

So this is more or less of what I'm trying:

I have an abstract class extracted out for all the common functionalities, Which includes a polymorphic association, so it looks like this:

class Card < ActiveRecord::Base
  self.abstract_class = true
  belongs_to :cardable, polymorphic: true
  ...
end

class Spell < Card
  ...
end

class Unit < Card
  ...
end

Now when i try to use polymorphic associations on this, something on the lines of:

  class Deck < ActiveRecord::Base
    has_many :cards, :as => :cardable
  end

  class Hand < ActiveRecord::Base
    has_many :cards, :as => :cardable
  end

The belongs_to part of things work fine, i.e. spell.cardable works perfectly as expected

However, because of the abstract class, has_many doesn't work well i.e. hand.cards or deck.cards always gives an empty ActiveRecord Association

Is this a workable model, or if not, what would be a better way to model this entire scenario?

Answer 1

@JoshKurien well it sounds like you've answered your own question "it does not need a corresponding table" but in your case aren't cards an actual table in your DB? If so, just get rid of this line as it's clearly breaking the polymorphism provided by ActiveRecord

self.abstract_class = true

Perhaps a better way is to just let each model class which has a database table be defined as a regular model. If you need shared behavior in your models, can you use model concerns and extend those models from a shared concern?

See How to use concerns in Rails 4

But there are some who think concerns are a bad design, in that case you may also want to check out https://github.com/AndyObtiva/super_module as another alternative.