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

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

Overview

Specify this act if you want to model a tree structure by providing a parent association and an children association. This act assumes that 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 
      \_ sub-child1

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

Instance Method Summary collapse

Instance Method Details

#acts_as_tree(options = {}) ⇒ Object

Configuration options are:

  • foreign_key - specifies the column name to use for track 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/tree.rb', line 35

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 => true

  module_eval <<-END
    def self.roots
      self.find(:all, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => "#{configuration[:order]}")
    end
    def self.root
      self.find(:first, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => "#{configuration[:order]}")
    end
  END

  define_method(:siblings) do
    if parent
      self.class.find(:all, :conditions => [ "#{configuration[:foreign_key]} = ?", parent.id ], :order => configuration[:order])
    else
      self.class.roots
    end
  end
end