acts_as_tree (for rails3)

Specify this acts_as extension if you want to model a tree structure by providing a parent association and a children
association. This requires that you have a foreign key column, which by default is called parent_id.

class Category < ActiveRecord::Base
  acts_as_tree :order => "name"
end

Example

root
 \_ child1
      \_ subchild1
      \_ subchild2

root      = Category.create("name" => "root")
child1    = root.children.create("name" => "child1")
subchild1 = child1.children.create("name" => "subchild1")

root.parent   # => nil
child1.parent # => root
root.children # => [child1]
root.children.first.children.first # => subchild1

Copyright © 2007 David Heinemeier Hansson, released under the MIT license