Question

I want to return results to a user sorted by a scoring algorithm that is personalized to the user based on their friends. For context, in my app, users have events that they can add to their calendar. Myevents is a join table between users and events. I want to calculate a score based on how many total attendees there are to an event and how many of a user’s friends are attending that event.

I want to do something like this:

class Event < ActiveRecord::Base

after_initialize :calculate_score
attr_accessor :score



  def calculate_score(user_id)


     User.find_by_id(user_id).friends.each do |friend|

                        if @id = Myevents.find_by_user_id_and_flier_id(friend.id, self.id)

                            friends_attending_list << @id
                        end

      end

    friends_attending_count = friends_attending_list.count

    total_attendees_count = Myevents.where(:flier_id => self.id, :attending_status => "1").count

     self.score = 100*(friend_attending_count) + 50*(total_attendees_count)

  end


end

Unfortunately, I can’t find a good way to pass the session’s user_id to the model….ideally, I would like to not violate MVC but I want to be able to sort results by this calculated score. Any advice?

Answer 1

First, to scale, you would need to cache this score somewhere. This method here would be veryyy expensive. But it’s not a simple problem since it’s a score per user per event.

I dont see how it makes sense to store the score on the event.

Without thinking of performances, I would have a score_for_event(event) method on the User model that you can call wherever you need.