Module ActsAsTree::ClassMethods
In: lib/acts_as_tree.rb

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

In addition to the parent and children associations, the following instance methods are added to the class after calling acts_as_tree:

  • siblings - Returns all the children of the parent, excluding the current node ([subchild2] when called on subchild1)
  • self_and_siblings - Returns all the children of the parent, including the current node ([subchild1, subchild2] when called on subchild1)
  • ancestors - Returns all the ancestors of the current node ([child1, root] when called on subchild2)
  • root - Returns the root of the current node (root when called on subchild2)

Methods

Public Instance methods

Configuration options are:

  • foreign_key - specifies the column name to use for tracking of the tree (default: parent_id)
  • order - makes it possible to sort the children according to this SQL snippet.
  • counter_cache - keeps a count in a children_count column if set to true (default: false).

[Validate]