gistfile1.rb

class Widget < ActiveRecord::Base
  # initialized contstant for the validator
  VALID_COLORS = %(red white blue)
  belongs_to :box
  has_many :categorizations
  has_many :categories, :through => :categorizations
  validates_presence_of :name
  validates_length_of :name, :minimum => 3
  validates_numericality_of :size

  validates :color, :inclusion => { :in => VALID_COLORS,
    :message => "can only be red white or blue" } 
    
  before_validation :downcase_color
  
  def downcase_color
    self.color.downcase!
  end
  
  def category_names
    categories.map {|c| c.cat_name}.to_sentence
  end
  
end