Module ActiveRecord::Acts::Tree::ClassMethods
In: vendor/rails/activerecord/lib/active_record/acts/tree.rb

Specify this act if you want to model a tree structure by providing a parent association and an children association. This act assumes that 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
        \_ sub-child1

  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

Methods

acts_as_tree  

Public Instance methods

acts_as_tree(options = {})

Configuration options are:

  • foreign_key - specifies the column name to use for track 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).

[Source]

    # File vendor/rails/activerecord/lib/active_record/acts/tree.rb, line 35
35:         def acts_as_tree(options = {})
36:           configuration = { :foreign_key => "parent_id", :order => nil, :counter_cache => nil }
37:           configuration.update(options) if options.is_a?(Hash)
38: 
39:           belongs_to :parent, :class_name => name, :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache]
40:           has_many :children, :class_name => name, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => true
41: 
42:           module_eval "def self.roots\nself.find(:all, :conditions => \"\#{configuration[:foreign_key]} IS NULL\", :order => \"\#{configuration[:order]}\")\nend\ndef self.root\nself.find(:first, :conditions => \"\#{configuration[:foreign_key]} IS NULL\", :order => \"\#{configuration[:order]}\")\nend\n"
43: 
44:           define_method(:siblings) do
45:             if parent
46:               self.class.find(:all, :conditions => [ "#{configuration[:foreign_key]} = ?", parent.id ], :order => configuration[:order])
47:             else
48:               self.class.roots
49:             end
50:           end
51:         end

[Validate]