app/models/seat.rb
class Seat < ActiveRecord::Base
has_one :ticket, dependent: :destroy
validates :table, :presence => true
validates :seat, :presence => true
validates :x, :presence => true
validates :y, :presence => true
validates_uniqueness_of :table, :scope => :seat
validates_uniqueness_of :x, :scope => :y
attr_accessor :ticket_type
attr_accessor :code
attr_accessor :given_away
end