Rails: includes with polymorphic association

Question

I read this interesting article about Using Polymorphism to Make a Better Activity Feed in Rails.

We end up with something like

class Activity < A         


        

Answer 1

image_activities = Activity.where(:subject_type => 'Image').includes(:subject => :tags).order(created_at: :desc).limit(20)
event_activities = Activity.where(:subject_type => 'Event').includes(:subject => :guests).order(created_at: :desc).limit(20)
activities = (image_activities + event_activities).sort_by(&:created_at).reverse.first(20)