class MigrateSlotsReservations < ActiveRecord::Migration def up Slot.all.each do |slot| SlotsReservation.create!({slot_id: slot.id, reservation_id: slot.reservation_id}) end end def down SlotsReservation.all.each do |sr| Slot.find(sr.slot_id).update_attributes(:reservation_id => sr.reservation_id) end end end