Keeping custom sorting across edit/update controller methods

I have an order

class Order < ActiveRecord::Base
has_many :order_items

with items

class OrderItem < ActiveRecord::Base
belongs_to :family
belongs_to :order
has_many :order_items

I sort the order items via a scope which joins with item family to

sort them accordingly
scope :default_order, joins(:family).order(‘,


def edit
@order = Order.find params[:id]
@ois = @order.order_items.default_order

My problem is in the update method, if we have errors and must show

the order to the user…

How do I sort properly my items?

def update

if @order.update_attributes(params[:order])

else #it doesn’t validate
#if I do
@ois = @order.order_items.default_order
# items are reloaded (with the correct order) BUT user input and
validation errors are lost.

How do I keep the sorting + data?!?

  • I don’t want to use a default_scope in order items because of
    problems I had with it in the past and performance.
  • Since my sorting is made over two models, I can’t use the
    basic :order on the has_many association.
    I guess the best would be to be able to assign a default_scope on the
    has_many association so when they are loaded implicitly (especially
    during @order.update_attributes(params[:order]) the order is

To show the pain and ugliness, I currently do this way.
@items = @order.order_items
@items = params[:order][:order_items_attributes]{|v|
v[:id]}.map{|id| @items.detect{|i| == id.to_i}} unless
It works because the params hash keeps the sorting order…

I really hope I’m doing something wrong and there is a better way…