Introduce an association for the selected_schedule

Association in Program fot the selected_schedule

db/migrate/20160704091928_create_schedules.rb

@@ -4,6 +4,6 @@ class CreateSchedules < ActiveRecord::Migration
       t.belongs_to :program, index: true
       t.timestamps null: false
     end
-    add_column :programs, :selected_schedule, :integer # Selected schedule ID
+    add_reference :programs, :selected_schedule, index: true
   end
 end