CODEWITHSUNDEEP
ruby-on-railsactiverecordruby-on-rails-4rails-activerecord
nanounanue
nanounanue

Reputation: 8342

How get all the objects in a polymorphic nested relationship in Rails 4

I have the following classes

class State < ActiveRecord::Base
  has_many :cities
  has_many :products, as: :geography
end

class City < ActiveRecord::Base
  has_many :neighborhoods
  has_many :products, as: :geography
end

class Neighborhood < ActiveRecord::Base
  has_many :products, as: :geography
end

class Product < ActiveRecord::Base
  belongs_to :geography, polymorphic: true
end

class User < ActiveRecord::Base
  belongs_to :state
end

And obviously I have another class User. The user just has permissions for see the products in his/her state (except if the user is admin, in which case he/she can see all the products) How I can get all the products of a User?

I tried to add some has_many, :through to State as follows

has_many :cities_activities, through: :cities, source: :products

has_many :neighborhoods_activities, through: :neighborhoods, source: :products

def owned_activities
  self.products + self.cities_activities + self.neighborhoods_activities
end

but owned_activities returns an Array not a ActiveRecord::Relation (I need some way of return a ActiveRecord::Relation, so I can apply on it chained scopes).

I am patching the code with if-blocks and the code is getting messing and ugly, How can I do this in a clean, rails way?

@JTG suggested using merge, but apparently it don't work in a nested way (or for more of three tables/models):

Started GET "/api/products.json?order=total_cost&page=1&per_page=18" for 127.0.0.1 at 2014-07-20 09:27:29 -0500
Processing by ProductsController#index as JSON
  Parameters: {"order"=>"total_cost", "page"=>"1", "per_page"=>"18"}
Geokit is using the domain: localhost
  User Load (0.4ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 1 ORDER BY "users"."id" ASC LIMIT 1
  Role Load (0.3ms)  SELECT "roles".* FROM "roles" WHERE "roles"."id" = $1 ORDER BY "roles"."id" ASC LIMIT 1  [["id", 5]]
  State Load (0.2ms)  SELECT "states".* FROM "states" WHERE "states"."id" = $1 ORDER BY "states"."id" ASC LIMIT 1  [["id", 17]]
   (9.2ms)  SELECT COUNT(*) FROM "products" INNER JOIN "cities" ON "products"."geography_id" = "cities"."id" AND "products"."geography_type" = 'City' INNER JOIN "polygons" ON "products"."geography_id" = "neighborhoods"."id
" AND "products"."geography_type" = 'Neighborhood' INNER JOIN "cities" ON "neighborhoods"."cities_id" = "cities"."id" WHERE "products"."geography_id" = $1 AND "products"."geography_type" = $2 AND "cities"."states_id" = $1  [["geography_id", 17], ["geography_type", "State"], ["states_id", 17]]
PG::DuplicateAlias: ERROR:  table name "cities" specified more than once
: SELECT COUNT(*) FROM "products" INNER JOIN "cities" ON "products"."geography_id" = "cities"."id" AND "products"."geography_type" = 'City' INNER JOIN "neighborhoods" ON "products"."geography_id" = "neighborhoods"."id" AND "products"."geography_type" = 'Neighborhood' INNER JOIN "cities" ON "neighborhoods"."cities_id" = "cities"."id" WHERE "products"."geography_id" = $1 AND "products"."geography_type" = $2 AND "cities"."states_id" = $1
ERROR:  table name "cities" specified more than once
 -- Clase:

Upvotes: 0

Views: 2118

Answers (2)

jokklan
jokklan

Reputation: 3540

You can't use merge will combine the queries with AND and what you need is a SQL OR query. That is unfortunately not supported by any ActiveRecord method. You can use arel to create this query, but as it will be very complex and contain a lot of subqueries do I find it easier to just find the id's you need with normal queries and then use those.

To do that can you implement something like this in State.

class State < ActiveRecord::Base
  has_many :cities
  has_many :neighborhoods, through: :cities

  has_many :products, as: :geography
  has_many :city_products, through: :cities, source: :products
  has_many :neighborhood_products, through: :neighborhoods, source: :products

  def all_products
    state_product_ids = product_ids
    city_product_ids = city_products.pluck(:id)
    neighborhood_product_ids = neighborhood_products.pluck(:id)
    all_product_ids = [state_product_ids, city_product_ids, neighborhood_product_ids].flatten.uniq

    Product.where(id: all_product_ids)
  end
end

You can now query a user for all products like this user.state.all_products.

Upvotes: 1

Blair Anderson
Blair Anderson

Reputation: 20171

A polymorphic association is not suited optimally for these relationships...

You can use a nested has_many.

class State < ActiveRecord::Base
  has_many :cities
  has_many :products, through: :cities
end

class City < ActiveRecord::Base
  has_many :neighborhoods
  has_many :products, through: :neighborhoods
end

class Neighborhood < ActiveRecord::Base
  has_many :products
end

class Product < ActiveRecord::Base
  belongs_to :neighborhood
end

class User < ActiveRecord::Base
  belongs_to :state
end

Then you should be able to run user.state.products

Even better would be to add has_many :products, through: :state to user.rb so you could run user.products

Upvotes: 1

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