Refactored sortable_by into a property instead of a classmethod.

Added backwards compatibility for pre 1.1.1 versions that still have sortable_by defined as a classmethod.
Need to address dynamic regroup template tag to see why categories are not being grouped properly in sample app.

adminsortable/admin.py

@@ -53,13 +53,18 @@ class SortableAdmin(ModelAdmin):
         has_perm = request.user.has_perm(opts.app_label + '.' + opts.get_change_permission())
         objects = self.model.objects.all()
 
-        """
-        Determine if we need to regroup objects relative to a foreign key specified on the
-        model class that is extending Sortable.
-        """
+        #Determine if we need to regroup objects relative to a foreign key specified on the
+        # model class that is extending Sortable.
         sortable_by = getattr(self.model, 'sortable_by', None)
         if sortable_by:
-            sortable_by_class, sortable_by_expression = sortable_by()
+            #backwards compatibility for < 1.1.1, where sortable_by was a classmethod instead of a property
+            try:
+                sortable_by_class, sortable_by_expression = sortable_by()
+            except ValueError:
+                sortable_by_class = self.model.sortable_by
+                sortable_by_expression = sortable_by_class.__name__.lower()
+
+            print sortable_by_expression
             sortable_by_class_display_name = sortable_by_class._meta.verbose_name_plural
             sortable_by_class_is_sortable = sortable_by_class.is_sortable()
         else:

adminsortable/models.py

@@ -14,8 +14,12 @@ class Sortable(models.Model):
     `model_type_id` returns the ContentType.id for the Model that inherits Sortable
 
     `save` the override of save increments the last/highest value of order by 1
+
+    Override `sortable_by` method to make your model be sortable by a foreign key field.
+    Set `sortable_by` to the class specified in the foreign key relationship.
     """
     order = models.PositiveIntegerField(editable=False, default=1, db_index=True)
+    sortable_by = None
 
     class Meta:
         abstract = True

adminsortable/templates/adminsortable/change_list.html

@@ -55,7 +55,7 @@
 		{% if objects %}
 		<div id="sortable">
 			{% if group_expression %}
-                            {% render_nested_sortable_objects objects group_expression %}
+                 {% render_nested_sortable_objects objects group_expression %}
 			{% else %}
 			     {% render_sortable_objects objects %}
 			{% endif %}

adminsortable/templatetags/django_template_additions.py

@@ -69,7 +69,7 @@ def dynamic_regroup(parser, token):
     """
     expression = lastbits_reversed[2][::-1]
     var_name = lastbits_reversed[0][::-1]
-
+    print expression
     """
     We also need to hand the parser to the node in order to convert the value
     for `expression` to a FilterExpression.