activerecord-sortable | gem activerecord-sortable allows | Application Framework library

# Gemfile

gem 'activerecord-sortable'
gem 'jquery-ui-rails' # if you plan to use drag and drop
# app/models/thing.rb

class Thing < ActiveRecord::Base
  acts_as_sortable
end
# db/migrate/20140512100816_create_things.rb

class CreateThings < Ac  

# app/models/parent.rb

class Parent < ActiveRecord::Base
  has_many :children, -> { ordered_by_position_asc }

  accepts_nested_attributes_for :children
end
# app/models/child.rb

class Child < ActiveRecord::Base
  acts_as_sortable do |conf  

# Gemfile

gem 'activerecord-sortable'
# db/migrate/20140525112125_add_position_to_items.rb

class AddPositionToItems < ActiveRecord::Migration
  def up
    add_column :items, :position, :integer

    # specify order
    Item.order('id desc').each