Module: ActiveRecord::Acts::HappyTree::ClassMethods

Defined in:
lib/active_record/acts/happy_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_happy_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_happy_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)

  • descendants - Returns a flat list of the descendants of the current node ([child1, subchild1, subchild2] when called on root)

Instance Method Summary collapse

Instance Method Details

#acts_as_happy_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/active_record/acts/happy_tree.rb', line 43

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

  belongs_to :parent, :class_name => name, :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache], :touch => configuration[:touch]
  has_many :children, :class_name => name, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => configuration[:dependent]

  validate :parent_key_must_be_valid

  class_eval <<-EOV
    include ActiveRecord::Acts::HappyTree::InstanceMethods
    include ActiveRecord::Acts::HappyTree::BreadthFirst
    include ActiveRecord::Acts::HappyTree::DepthFirst

    scope :roots, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}}

    after_update :update_parents_counter_cache

    def self.root
      roots.first
    end

    def self.childless
      nodes = []

      find(:all).each do |node|
        nodes << node if node.children.empty?
      end

      nodes
    end

    def self.parent_key
      "#{configuration[:foreign_key]}"
    end
  EOV
end

#children_of(node_ids, options = {}) ⇒ Object 



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# File 'lib/active_record/acts/happy_tree.rb', line 107

def children_of(node_ids, options={})
  where(parent_key=>node_ids).apply_finder_options(options)
end

#pluck_child_ids_of(node_ids, options = {}) ⇒ Object 



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# File 'lib/active_record/acts/happy_tree.rb', line 86

def pluck_child_ids_of(node_ids, options={})
  where(parent_key=>node_ids).apply_finder_options(options).pluck(:id)
end

#pluck_parent_id_of(node_id) ⇒ Object

AR >= 3.2 only



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# File 'lib/active_record/acts/happy_tree.rb', line 82

def pluck_parent_id_of(node_id)
  where(:id=>node_id).pluck(parent_key).first
end

#select_child_ids_of(node_ids, options = {}) ⇒ Object Also known as: child_ids_of 



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# File 'lib/active_record/acts/happy_tree.rb', line 95

def select_child_ids_of(node_ids, options={})
  where(parent_key=>node_ids).apply_finder_options(options.merge(:select=>:id)).map(&:id)
end

#select_parent_id_of(node_id) ⇒ Object Also known as: parent_id_of

AR >= 3.0 only



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# File 'lib/active_record/acts/happy_tree.rb', line 91

def select_parent_id_of(node_id)
  where(:id=>node_id).select(parent_key).first[parent_key]
end