gistfile1.rb

# the migration
class CreateForumPosts < ActiveRecord::Migration
  def self.up
    create_table :forum_posts do |t|
      t.string :title
      t.text :message
      t.integer :parent_id

      t.timestamps
    end
  end

  def self.down
    drop_table :forum_posts
  end
end

# the model
class ForumPost < ActiveRecord::Base
  has_many :children, :class_name => "ForumPost", :foreign_key => :parent_id, :select => "id, parent_id, title"
  belongs_to :parent, :class_name => "ForumPost", :foreign_key => :parent_id, :select => "id, parent_id, title"
end