Rails polymorphic has_many :through

Question

I'm pulling some data from an external API and would like to cache the results locally. I have a class SearchTerm, which I would like to be associated with a few different ActiveRecord types through the table searchable_items. I'm pretty sure I have the tables set up correctly, but something in my associations must be wrong.

class Foo < ActiveRecord::Base
  has_many :search_terms, :as => :searchable, :through => :searchable_items
end

class Bar < ActiveRecord::Base
  has_many :search_terms, :as => :searchable, :through => :searchable_items
end

class SearchTerm < ActiveRecord::Base
  has_many :searchables, :through => :searchable_items
end

class SearchableItem < ActiveRecord::Base
  belongs_to :search_term
  belongs_to :searchable, :polymorphic => true
end

I would expect to be able to do something like SearchTerm.find_by_term('SearchTerm').searchables (and it would return an array of Foo and Bar objects) however, I get the error Could not find the association :searchable_items in model SearchTerm

Thanks in advance for any insight you can provide to me!

Toxinantitoxin

Answer 1

You need to add has_many :searchable_items association to Foo, Bar and SearchTerm models because :through => :searchable_items option refers to that association.

http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association

Vituperate

Unfortunately, adding what you suggested gives Cannot have a has_many :through association 'SearchTerm#searchables' on the polymorphic object 'Searchable#searchable'. – Toxinantitoxin

Similar setup here: #1683765 – Vituperate

Like the error message says, you cannot have has many through association on polymorpic object. You could have separate has many throughs for Foo and Bar like in the linked question above. – Vituperate

The linked question is exactly what I was looking for. Thanks Heikki. – Toxinantitoxin