gistfile1.rb

class User < ActiveRecord::Base

  before_create :create_profile
  has_one :profile, :dependent => :destroy

  protected
    def create_profile
      self.profile ||= Profile.new
    end
end

class Profile < ActiveRecord::Base
  after_create :create_root_graffity
  belongs_to :user
  has_one :root_graffity, :class_name => 'Comment', :as => :commentable, :conditions => "parent_id IS NULL"

  def graffities
    root_graffity.sons
  end

  protected
    def create_root_graffity
      self.root_graffity = Comment.new(:user => self.user)
      self.save(false)
    end
end

class Comment < ActiveRecord::Base
  acts_as_nested_set :scope => [:commentable_id, :commentable_type]
  
  validates_presence_of :body
  validates_presence_of :user
  
  # NOTE: install the acts_as_votable plugin if you 
  # want user to vote on the quality of comments.
  #acts_as_voteable
  
  # NOTE: Comments belong to a user
  belongs_to :user
  belongs_to :commentable, :polymorphic => true

  has_many :sons, :class_name => 'Comment',
              :foreign_key => "parent_id", :order => "created_at DESC"
  has_many :replys, :class_name => "Comment",
              :foreign_key => "parent_id", :order => "created_at ASC"

  # EXTRA CODE HERE
end