Chris@1295: module ActiveRecord Chris@1295: module Acts Chris@1295: module Tree Chris@1295: def self.included(base) Chris@1295: base.extend(ClassMethods) Chris@1295: end Chris@1295: Chris@1295: # Specify this +acts_as+ extension if you want to model a tree structure by providing a parent association and a children Chris@1295: # association. This requires that you have a foreign key column, which by default is called +parent_id+. Chris@1295: # Chris@1295: # class Category < ActiveRecord::Base Chris@1295: # acts_as_tree :order => "name" Chris@1295: # end Chris@1295: # Chris@1295: # Example: Chris@1295: # root Chris@1295: # \_ child1 Chris@1295: # \_ subchild1 Chris@1295: # \_ subchild2 Chris@1295: # Chris@1295: # root = Category.create("name" => "root") Chris@1295: # child1 = root.children.create("name" => "child1") Chris@1295: # subchild1 = child1.children.create("name" => "subchild1") Chris@1295: # Chris@1295: # root.parent # => nil Chris@1295: # child1.parent # => root Chris@1295: # root.children # => [child1] Chris@1295: # root.children.first.children.first # => subchild1 Chris@1295: # Chris@1295: # In addition to the parent and children associations, the following instance methods are added to the class Chris@1295: # after calling acts_as_tree: Chris@1295: # * siblings - Returns all the children of the parent, excluding the current node ([subchild2] when called on subchild1) Chris@1295: # * self_and_siblings - Returns all the children of the parent, including the current node ([subchild1, subchild2] when called on subchild1) Chris@1295: # * ancestors - Returns all the ancestors of the current node ([child1, root] when called on subchild2) Chris@1295: # * root - Returns the root of the current node (root when called on subchild2) Chris@1295: module ClassMethods Chris@1295: # Configuration options are: Chris@1295: # Chris@1295: # * foreign_key - specifies the column name to use for tracking of the tree (default: +parent_id+) Chris@1295: # * order - makes it possible to sort the children according to this SQL snippet. Chris@1295: # * counter_cache - keeps a count in a +children_count+ column if set to +true+ (default: +false+). Chris@1295: def acts_as_tree(options = {}) Chris@1295: configuration = { :foreign_key => "parent_id", :dependent => :destroy, :order => nil, :counter_cache => nil } Chris@1295: configuration.update(options) if options.is_a?(Hash) Chris@1295: Chris@1295: belongs_to :parent, :class_name => name, :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache] Chris@1295: has_many :children, :class_name => name, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => configuration[:dependent] Chris@1295: Chris@1295: scope :roots, where("#{configuration[:foreign_key]} IS NULL").order(configuration[:order]) Chris@1295: Chris@1295: send :include, ActiveRecord::Acts::Tree::InstanceMethods Chris@1295: end Chris@1295: end Chris@1295: Chris@1295: module InstanceMethods Chris@1295: # Returns list of ancestors, starting from parent until root. Chris@1295: # Chris@1295: # subchild1.ancestors # => [child1, root] Chris@1295: def ancestors Chris@1295: node, nodes = self, [] Chris@1295: nodes << node = node.parent while node.parent Chris@1295: nodes Chris@1295: end Chris@1295: Chris@1295: # Returns list of descendants. Chris@1295: # Chris@1295: # root.descendants # => [child1, subchild1, subchild2] Chris@1295: def descendants(depth=nil) Chris@1295: depth ||= 0 Chris@1295: result = children.dup Chris@1295: unless depth == 1 Chris@1295: result += children.collect {|child| child.descendants(depth-1)}.flatten Chris@1295: end Chris@1295: result Chris@1295: end Chris@1295: Chris@1295: # Returns list of descendants and a reference to the current node. Chris@1295: # Chris@1295: # root.self_and_descendants # => [root, child1, subchild1, subchild2] Chris@1295: def self_and_descendants(depth=nil) Chris@1295: [self] + descendants(depth) Chris@1295: end Chris@1295: Chris@1295: # Returns the root node of the tree. Chris@1295: def root Chris@1295: node = self Chris@1295: node = node.parent while node.parent Chris@1295: node Chris@1295: end Chris@1295: Chris@1295: # Returns all siblings of the current node. Chris@1295: # Chris@1295: # subchild1.siblings # => [subchild2] Chris@1295: def siblings Chris@1295: self_and_siblings - [self] Chris@1295: end Chris@1295: Chris@1295: # Returns all siblings and a reference to the current node. Chris@1295: # Chris@1295: # subchild1.self_and_siblings # => [subchild1, subchild2] Chris@1295: def self_and_siblings Chris@1295: parent ? parent.children : self.class.roots Chris@1295: end Chris@1295: end Chris@1295: end Chris@1295: end Chris@1295: end