Add track_id to Event

app/models/event.rb

@@ -1,8 +1,8 @@
 class Event < ActiveRecord::Base
   include Proposable
 
-  has_one :track, through: :proposition, source: :proposition_accepting, source_type: Track
   belongs_to :conference
+  belongs_to :track
 
   has_many :participations
   has_many :pending_participations, ->() { pending }, class_name: 'Participation'

app/models/track.rb

@@ -2,7 +2,7 @@ class Track < ActiveRecord::Base
   include PropositionAccepting
 
   belongs_to :conference
-  has_many :events, through: :propositions, source: :proposable, source_type: Event
+  has_many :events
 
   validates :name, presence: true
   validates :color, presence: true, format: {with: /\A#?[a-f0-9]{6}\z/i}

db/migrate/20150814203341_add_track_id_to_events.rb

@@ -0,0 +1,21 @@
+class Event < ActiveRecord::Base
+  has_one :proposition, as: :proposable
+end
+
+class Proposition < ActiveRecord::Base
+  belongs_to :proposable, polymorphic: true
+end
+
+class AddTrackIdToEvents < ActiveRecord::Migration
+  def up
+    add_reference :events, :track, index: true, foreign_key: true
+
+    Event.all.includes(:proposition).each do |event|
+      event.update!(track_id: event.proposition.proposition_accepting_id)
+    end
+  end
+
+  def down
+    remove_reference :events, :track, index: true, foreign_key: true
+  end
+end