Rails 3 fields_for - sort order gets lost

问题

I am using Rails 3.0.3 with ruby 1.9.2p0.

In my profiles_controller (edit function) I have this call

@profile = Profile.find(params[:id])
@profile_items = @profile.profile_items.order("pos")

to get the @profile_items in the correct order, sorted on "pos". In the _form.html.erb I have the following

<% @profile_items.each do |pi| %>
  <%= pi.pos %> | 
<% end %>
<%= f.fields_for :profile_items do |f2| %>
  <%= render 'profile_item_fields', :f => f2 %>
<% end %>

The 3 first lines are test code to show that the @profile_items are in the correct order. But when they are rendered they have lost the sorted order!

Now I have search a lot for an answer and I think this must be a common "trap" to fall into.

Thankful for any help...

回答1:

According to the Rails Documentation for fields_for, you can also specify the record object after the record name.

So something like this should work...

<%= f.fields_for :profile_items, @profile_items do |f2| %>
  <%= render 'profile_item_fields', :f => f2 %>
<% end %>

回答2:

This can be accomplished with a default_scope on the nested model:

class YourModel < ActiveRecord::Base
  belongs_to :other_model
  default_scope { order(:name) }
end

来源：https://stackoverflow.com/questions/4961832/rails-3-fields-for-sort-order-gets-lost