acts_as_tree
============
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 (c) 2007 David Heinemeier Hansson, released under the MIT license
Includes patch from http://dev.rubyonrails.org/ticket/1924