Add conference_id to Event

app/models/event.rb

@@ -2,7 +2,7 @@ class Event < ActiveRecord::Base
   include Proposable
 
   has_one :track, through: :proposition, source: :proposition_accepting, source_type: Track
-  has_one :conference, through: :track
+  belongs_to :conference
 
   has_many :participations
   has_many :pending_participations, ->() { pending }, class_name: 'Participation'

db/migrate/20150814202053_add_conference_id_to_events.rb

@@ -0,0 +1,25 @@
+class Event < ActiveRecord::Base
+  has_one :proposition, as: :proposable
+end
+
+class Proposition < ActiveRecord::Base
+  belongs_to :proposable, polymorphic: true
+  belongs_to :proposition_accepting, polymorphic: true
+end
+
+class Track < ActiveRecord::Base
+end
+
+class AddConferenceIdToEvents < ActiveRecord::Migration
+  def up
+    add_reference :events, :conference, index: true, foreign_key: true
+
+    Event.all.includes(:proposition).each do |event|
+      event.update!(conference_id: event.proposition.proposition_accepting.conference_id)
+    end
+  end
+
+  def down
+    remove_reference :events, :conference, index: true, foreign_key: true
+  end
+end