Rails ActiveRecord: selecting and sorting on a dynamic field

I have two models, one is Group, the other Item.

A group has many items.

I'm trying to run a query on groups, and return the number of items for each group as a method of the group object.

The view should be :

<% @groups.each do |group| %>
   <tr><td><%= group.name %></td><td><%=开发者_高级运维 group.items_count %></td> ... and other fields
<% end %>

I'd like to be able to do a Group.where().page call including the dynamic attribute items_count, and be able to sort results by item_count, just as a standard attribute from the sql table. how can I do that in a simple way ?

The easiest way is probably to fetch the groups you need without a specific ordering, and then sort them in your controller afterwards:

def my_action
  @groups = Group.all()  # or Group.where(...) for more specific filtering
  @groups.sort! { |g1, g2| g1.items_count <=> g2.items_count }
  ...
end