Question

I have following models:

Product:

class Product < ActiveRecord::Base
  has_many :product_recommendations, :dependent => :destroy
  has_many :recommendations, :through => :product_recommendations  
end

ProductRecommendation:

class ProductRecommendation < ActiveRecord::Base
  belongs_to :recommendation
  belongs_to :product
end

Recommendation:

class Recommendation < ActiveRecord::Base
  has_many :product_recommendations, :dependent => :destroy
  has_many :products, :through => :product_recommendations

  has_many :recommendation_ratings, :dependent => :destroy
  has_many :ratings, :through => :recommendation_ratings
end

Rating:

class Rating < ActiveRecord::Base
  has_many :recommendation_ratings, :dependent => :destroy
  has_many :recommendations, :through => :recommendation_ratings
end

RecommendationRating:

class RecommendationRating < ActiveRecord::Base
  belongs_to :recommendation
  belongs_to :rating  
end

How would I be able to calculate the average rating for a given recommendation? My ratings table contains just 4 records, (Ratings 1-4), and I have an action in my recommendation controller which updates the RecommendationsRatings join table to associate a rating with a recommendation. Thanks!

Answer 1

have you tried:

class Product < ActiveRecord::Base
  has_many :product_recommendations, :dependent => :destroy
  has_many :recommendations, :through => :product_recommendations
  has_many :ratings, :through => :recommendations
end

and then

p = Product.find 1
p.ratings.average(:rating)  

this is assuming the Ratings model has an int / float called rating which stores the rating