Problems with associations and sorting

rubyonrails-talk
1

I have the following code that always fails with "comparison of String with 0 failed". Here's the sort I'm trying to do:

orders = SalesOrder.find(:all, :include => [:latest_type]).sort{ |a,b|   if a.latest_type.nil? and b.latest_type.nil?; 0   elsif a.latest_type.nil?; 1   elsif b.latest_type.nil?; -1   else; b.latest_type.type_id <=> a.latest_type.type_id   end }

This never works, and I can't figure out why. I think it has something to do with my associations (and their schemas):

class SalesOrder < ActiveRecord::Base   has_one :latest_type,   :class_name => "TypeEvent",   :order => "created_at desc" end

class TypeEvent < ActiveRecord::Base   belongs_to :type   belongs_to :sales_order end

class Type < ActiveRecord::Base   has_many :type_events end

create_table "type_events", :force => true do |t|   t.column "sales_order_id", :integer   t.column "type_id", :integer   t.column "created_at", :datetime end

create_table "types", :force => true do |t|   t.column "type_name", :string end

Can anyone help me, or at least point me in a direction here? I would really like to compare by latest_type.type.type_name, but I can't figure out how to do it.