Question

我有以下模特：

产品：

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

建议：

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

评分：

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

我如何计算给定建议的平均评分？我的评级表只包含4条记录，（评级1-4），我在推荐控制器中有一个操作，它更新了RecommendationsRatings连接表，将评级与推荐相关联。谢谢！

Answer 1

你试过了吗？

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

然后

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

这是假设Ratings模型有一个名为rating / int的int / float来存储评级

Rails使用has_many通过关系查找和计算

1 个答案: