Good Bike models for my mongoid talk at RORO

bike.rb

class Bike
  include Mongoid::Document

  field :brand_name
  validates :brand_name, presence: true

  STYLES = %w(CARBON_MONSTROSITY DUALIE FIXIE TOURER)
  field :style
  validates :style, inclusion: STYLES

  field :colour

  field :price, type: BigDecimal

  embeds_many :parts, cascade_callbacks: true

  # indexes
  index brand_name: 1
  index style: 1
  index colour: 1
  index price: 1
  index brand_name: 1, style: 1
  index 'parts.brand_name' => 1

  # scopes
  scope :sram_cranks, ->(){
    where( 'parts.name' => 'CRANK',
           'parts.brand_name' => 'SRAM')
  }

end

part.rb

class Part
  include Mongoid::Document

  embedded_in :bike

  field :name
  validates :name, presence: true

  field :brand_name

  field :colour
  validates :colour, presence: true

  before_save :upcase_colour

  def upcase_colour
    self.colour = colour.upcase
  end
end