Module: ActiveRecord::Acts::Tree::ClassMethods

Defined in:
lib/plugins/acts_as_tree/lib/active_record/acts/tree.rb

Overview

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)

Instance Method Summary collapse

Instance Method Details

#acts_as_tree(options = {}) ⇒ Object

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).


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# File 'lib/plugins/acts_as_tree/lib/active_record/acts/tree.rb', line 44

def acts_as_tree(options = {})
  configuration = { :foreign_key => "parent_id", :dependent => :destroy, :order => nil, :counter_cache => nil }
  configuration.update(options) if options.is_a?(Hash)

  belongs_to :parent, :class_name => name, :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache]
  has_many :children, lambda {order(configuration[:order])}, :class_name => name, :foreign_key => configuration[:foreign_key], :dependent => configuration[:dependent]

  scope :roots, lambda {
                  where("#{configuration[:foreign_key]} IS NULL").
                    order(configuration[:order])
                }
  send :include, ActiveRecord::Acts::Tree::InstanceMethods
end