Specify this act if you want to model a tree structure by providing a parent association and a children association. This act 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 specifying the act:
- siblings : Returns all the children of the parent, excluding the current node ([ subchild2 ] when called from subchild1)
- self_and_siblings : Returns all the children of the parent, including the current node ([ subchild1, subchild2 ] when called from subchild1)
- ancestors : Returns all the ancestors of the current node ([child1, root] when called from subchild2)
- root : Returns the root of the current node (root when called from 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).
[ show source ]
# File vendor/rails/activerecord/lib/active_record/acts/tree.rb, line 42 42: def acts_as_tree(options = {}) 43: configuration = { :foreign_key => "parent_id", :order => nil, :counter_cache => nil } 44: configuration.update(options) if options.is_a?(Hash) 45: 46: belongs_to :parent, :class_name => name, :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache] 47: has_many :children, :class_name => name, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => :destroy 48: 49: class_eval "include ActiveRecord::Acts::Tree::InstanceMethods\n\ndef self.roots\nfind(:all, :conditions => \"\#{configuration[:foreign_key]} IS NULL\", :order => \#{configuration[:order].nil? ? \"nil\" : %Q{\"\#{configuration[:order]}\"}})\nend\n\ndef self.root\nfind(:first, :conditions => \"\#{configuration[:foreign_key]} IS NULL\", :order => \#{configuration[:order].nil? ? \"nil\" : %Q{\"\#{configuration[:order]}\"}})\nend\n" 50: end