Merged pull request #51 from thinkcast/master.

Removed hardcoded primary key from versions

lib/paper_trail/has_paper_trail.rb

@@ -41,7 +41,7 @@ def has_paper_trail(options = {})
         cattr_accessor :paper_trail_enabled_for_model
         self.paper_trail_enabled_for_model = true
 
-        has_many :versions, :class_name => version_class_name, :as => :item, :order => 'created_at ASC, id ASC'
+        has_many :versions, :class_name => version_class_name, :as => :item, :order => "created_at ASC, #{self.primary_key} ASC"
 
         after_create  :record_create
         before_update :record_update

lib/paper_trail/version.rb

@@ -7,16 +7,16 @@ def self.with_item_keys(item_type, item_id)
   end
 
   scope :subsequent, lambda { |version|
-    where(["id > ?", version.is_a?(self) ? version.id : version]).order("id ASC")
+    where(["#{self.primary_key} > ?", version.is_a?(self) ? version.id : version]).order("#{self.primary_key} ASC")
   }
 
   scope :preceding, lambda { |version|
-    where(["id < ?", version.is_a?(self) ? version.id : version]).order("id DESC")
+    where(["#{self.primary_key} < ?", version.is_a?(self) ? version.id : version]).order("#{self.primary_key} DESC")
   }
 
   scope :after, lambda { |timestamp|
     # TODO: is this :order necessary, considering its presence on the has_many :versions association?
-    where(['created_at > ?', timestamp]).order('created_at ASC, id ASC')
+    where(['created_at > ?', timestamp]).order("created_at ASC, #{self.primary_key} ASC")
   }
 
   # Restore the item from this version.