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module ActiveRecord
module Acts
module Tree
def self.included(base)
base.extend(ClassMethods)
end
# 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 <tt>acts_as_tree</tt>:
# * <tt>siblings</tt> - Returns all the children of the parent, excluding the current node (<tt>[subchild2]</tt> when called on <tt>subchild1</tt>)
# * <tt>self_and_siblings</tt> - Returns all the children of the parent, including the current node (<tt>[subchild1, subchild2]</tt> when called on <tt>subchild1</tt>)
# * <tt>ancestors</tt> - Returns all the ancestors of the current node (<tt>[child1, root]</tt> when called on <tt>subchild2</tt>)
# * <tt>root</tt> - Returns the root of the current node (<tt>root</tt> when called on <tt>subchild2</tt>)
module ClassMethods
# Configuration options are:
#
# * <tt>foreign_key</tt> - specifies the column name to use for tracking of the tree (default: +parent_id+)
# * <tt>order</tt> - makes it possible to sort the children according to this SQL snippet.
# * <tt>counter_cache</tt> - keeps a count in a +children_count+ column if set to +true+ (default: +false+).
def acts_as_tree(options = {})
configuration = { :foreign_key => "parent_id", :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, :class_name => name, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => :destroy
class_eval <<-EOV
include ActiveRecord::Acts::Tree::InstanceMethods
def self.roots
find(:all, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}})
end
def self.root
find(:first, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}})
end
EOV
end
end
module InstanceMethods
# Returns list of ancestors, starting from parent until root.
#
# subchild1.ancestors # => [child1, root]
def ancestors
node, nodes = self, []
nodes << node = node.parent while node.parent
nodes
end
# Returns the root node of the tree.
def root
node = self
node = node.parent while node.parent
node
end
# Returns all siblings of the current node.
#
# subchild1.siblings # => [subchild2]
def siblings
self_and_siblings - [self]
end
# Returns all siblings and a reference to the current node.
#
# subchild1.self_and_siblings # => [subchild1, subchild2]
def self_and_siblings
parent ? parent.children : self.class.roots
end
end
end
end
end