Ruby on Rails Sortable/Reorderable lists on STI models using ranked_model, Twitter Bootstrap and inherited_resources

_index.html.haml

%h1= "Listing " + "#{resource_name}s"

.btn-group.pull-right
  = link_to "All #{resource_name(item: resource_class.superclass)}s", polymorphic_path([:admin, resource_class.superclass]), class: 'btn'
  = link_to "Add #{resource_name}", new_resource_path, class: 'btn-primary btn'

%br
%br

%table.table.table-bordered.table-striped#sortable{:data => {update_url: polymorphic_path([:sort, :admin, resource_class])}}
  %thead
    %tr
      - attributes.each do |attr|
        %th= resource_class.human_attribute_name(attr)
      %th  

  %tbody
    - collection.each do |resource|
      %tr{data: {item_id: "#{resource.id}"}, class: 'item'}
        - attributes.each do |attr|
          %td= resource.public_send(attr).to_s.truncate(20)
        %td
          = link_to 'show', resource_path(resource), :class => 'btn'
          = link_to 'edit', edit_resource_path(resource), :class => 'btn btn-primary'
          = link_to 'destroy', resource_path(resource), method: :delete, confirm: "Are you sure?", :class => 'btn btn-danger'

application.css.scss

#sortable {
  tr {
    cursor: row-resize;
  }
}

menu_items.js.coffee

jQuery ->
  #this is a fix; when a tr is dragged with jQuery UI sortable
  #the cells lose their width
  cells = $('.table').find('tr')[0].cells.length
  desired_width = 940 / cells + 'px'
  $('.table td').css('width', desired_width)

  $('#sortable').sortable(
    axis: 'y'
    items: 'tr'
    stop: (e, ui) ->
      ui.item.children('td').effect('highlight', {}, 1000)
    update: (e, ui) ->
      item_id = ui.item.data('item_id')
      position = ui.item.index()
      $.ajax(
        type: 'POST'
        url: $(this).data('update_url')
        dataType: 'json'
        data: { id: item_id, menu_item: { row_order_position: position } }
      )
  )

resource_helper.rb

module Admin::ResourcesHelper

  def attributes
    resource_class.attribute_names - %w(id created_at updated_at row_order)
  end

  # resource_class is an inherited_resources helper method
  # resource_name(item: resource_class.superclass) # => Menu Item (from a model that inherits from MenuItem)
  # resource_name # => Burger
  def resource_name(options = {})
    options[:item] ||= resource_class
    options[:item].name.underscore.humanize.titleize
  end

end

resources_controller.rb

class Admin::ResourcesController < Admin::ApplicationController
  inherit_resources
  respond_to :html

  def sort
    @menu_item = resource_class.find(params[:id])
    @menu_item.attributes = params[:menu_item]
    @menu_item.save
    render nothing: true
  end

  protected

  def collection
    collection_variable_name = controller_name.gsub(/^/, '@').to_sym
    instance_variable_set(collection_variable_name, resource_class.rank(:row_order).all)
  end
end

http://railscasts.com/episodes/269-template-inheritance
http://guides.rubyonrails.org/3_1_release_notes.html#action-dispatch
http://iain.nl/backends-in-rails-3-1
https://github.com/josevalim/inherited_resources

http://ruby-doc.org/core-1.9.3/Object.html#method-i-instance_variable_set