Ruby on Rails
ActsAsList

ActsAsList provides the capabilities for sorting and reordering a number of objects in list. The class that has this specified needs to have a “position” column defined as an integer on the mapped database table¹.

Todo list example:

  class TodoList < ActiveRecord::Base
    has_many :todo_items, :order => "position" 
  end

  class TodoItem < ActiveRecord::Base
    belongs_to :todo_list
    acts_as_list :scope => :todo_list
  end

  todo_list.first.move_to_bottom
  todo_list.last.move_higher

API documentation

• ActiveRecord::Acts::List::ClassMethods
• ActiveRecord::Acts::List::InstanceMethods

Examples

• Hierakis Chapter and Page models. See also the interesting implementation of “up/down/top/bottom” in the chapter controller
• s5presents Slide model(app\models\slide.rb) and controller(app\controllers\slide_controller.rb)

¹ Taken directly from the API