Added ActiveRecord::Mixins::List that can decorates an existing class with...

Added ActiveRecord::Mixins::List that can decorates an existing class with methods like move_higher/lower, move_to_top/bottom

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@84 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *CVS*
 
+* Added ActiveRecord::Mixins::List that can decorates an existing class with methods like move_higher/lower, move_to_top/bottom. Example:
+
+    class TodoItem < ActiveRecord::Base
+      include ActiveRecord::Mixins::List
+      belongs_to :todo_list
+   
+      private
+        def scope_condition
+          "todo_list_id = #{todo_list_id}"
+        end
+    end
+  
 * Added the option for sanitizing find_by_sql and the offset parts in regular finds [Sam Stephenson]. Examples:
 
     Project.find_all ["category = ?", category_name], "created ASC", ["? OFFSET ?", 15, 20]

activerecord/lib/active_record/mixins/list.rb

 module ActiveRecord
+  # Mixins are a way of decorating existing Active Record models with additional behavior. If you for example
+  # want to keep a number of Documents in order, you can include Mixins::List, and all of the sudden be able to
+  # call <tt>document.move_to_bottom</tt>.
   module Mixins
     # This mixin provides the capabilities for sorting and reordering a number of objects in list.
     # The class that has this mixin included needs to have a "position" column defined as an integer on
@@ -12,7 +15,7 @@ module Mixins
     #   end
     #
     #   class TodoItem < ActiveRecord::Base
-    #     include ListMixin
+    #     include ActiveRecord::Mixins::List
     #     belongs_to :todo_list
     #  
     #     private