Question

I have 2 models Product and Tag with many-to-many relationship.

class Product < ActiveRecord::Base
  has_many :product_tags
  has_many :tags, through: :product_tags
end

class Tag < ActiveRecord::Base
  has_many :product_tags
  has_many :products, through: :product_tags
end

and the relationship model:

class ProductTag < ActiveRecord::Base
  belongs_to :product
  belongs_to :tag
end

What would be the most optimal way to search for the products by the list of given tags? The products must have all the tags, not just one of them.

Answer 1

I found the answer here https://stackoverflow.com/a/11887362/808175. So in my case it is:

tags = ['1', '2', '3']
Product.joins(:tags)
       .where(:tags => {:id => tags})
       .group('products.id')
       .having("count(product_tags.tag_id) = #{tags.count}")