http://stackoverflow.com/questions/5109893/rails-how-do-self-referential-has-many-models-work
belongs_to :parent, :class_name => "Folder" has_many :folders, :foreign_key => "parent_id"
http://stackoverflow.com/questions/5109893/rails-how-do-self-referential-has-many-models-work
belongs_to :parent, :class_name => "Folder" has_many :folders, :foreign_key => "parent_id"