bike-database/app/models/bike.rb

class Bike < ActiveRecord::Base
  validates :log_number, presence: true
  validates :brand, presence: true
  validates :model, presence: true
  validates :bike_type, presence: true
  validates :color, presence: true
  validates :serial_number, presence: true

  def name
    [self.seat_tube_size.to_s, self.brand, self.model] * ' '
  end
end