Module: ActsAsTree::ClassMethods

Defined in:
lib/acts_as_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/acts_as_tree.rb', line 42

def acts_as_tree(options = {})
  configuration = { :foreign_key => "parent_id", :order => nil, :counter_cache => nil, :after_add => [], :before_add => [], :after_remove => [], :before_remove => [] }
  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, :class_name => name, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => :destroy, :before_add => configuration[:before_add], :after_add => configuration[:after_add], :before_remove => configuration[:before_remove], :after_remove => configuration[:after_remove]

  class_eval "    include ActsAsTree::InstanceMethods\n\n    def self.roots\n      find(:all, :conditions => \"\#{configuration[:foreign_key]} IS NULL\", :order => \#{configuration[:order].nil? ? \"nil\" : %Q{\"\#{configuration[:order]}\"}})\n    end\n\n    def self.root\n      find(:first, :conditions => \"\#{configuration[:foreign_key]} IS NULL\", :order => \#{configuration[:order].nil? ? \"nil\" : %Q{\"\#{configuration[:order]}\"}})\n    end\n  EOV\nend\n"