Task.rb

class Task < ActiveRecord::Base
  has_many :assets, :as => :attachable, :dependent => :destroy
  
  validate :validate_attachments
  
  Max_Attachments = 5
  Max_Attachment_Size = 1.megabyte

  def validate_attachments
    errors.add_to_base("You should attach at least one file") if assets.nil?
    return if assets.nil?
    errors.add_to_base("Too many attachments - maximum is #{Max_Attachments}") if assets.length > Max_Attachments
    assets.each {|a| errors.add_to_base("#{a.name} is over #{Max_Attachment_Size/1.megabyte}MB") if a.file_size > Max_Attachment_Size}
  end


end