Question

I have a jquery sortable calling a data-update-url in my model controller, everything is good and the function is getting called.
my sort function

def sort
        params[:documents].each_with_index do |id, index|
            Document.update_all({position: index+1}, {id: id})
        end
        render nothing: true
    end

Now i’m using mongoid and I know there isn’t exactly as flexible way to do what I want as you can in SQL. After a user drags an element in the list the way he wants, I want the positon to update so the order of the users list is persistent through sessions.
The above function was a template I started so I can start in the right direction (from railscasts)
My first problem is the params[:documents].each_with_index, im gettting thrown a

NoMethodError (undefined method `each_with_index' for nil:NilClass):
  app/controllers/documents_controller.rb:16:in `sort'

So i’m sure params[:document] isn’t what i want to pass to the each_with_index method but i’m unsure what to try?

update
document.js.coffee

jQuery ->
  $('#documents').sortable(
    update: ->
      $.post($(this).data('update-url'), $(this).sortable('serialize')));

corresponding erb

<ul id="documents" data-update-url="<%= sort_documents_url %>">
  <% @documents.each do |document| %>
    <%= content_tag_for :li, document do %>
      <%= render document %>
    <% end %>
  <% end %>

Answer 1

def sort
    params[:documents].each_with_index do |id, index|
      doc = Document.find_by_id(id)
      doc.update_attribute(:position, index) if doc
    end
    render nothing: true
end