Ticket #10263: inlineformset_factory_order_by.diff

django-trunk/django/forms/models.py

@@ -462 +462 @@
 class BaseInlineFormSet(BaseModelFormSet):
     """A formset for child objects related to a parent."""
     def __init__(self, data=None, files=None, instance=None,
-                 save_as_new=False, prefix=None):
+                 save_as_new=False, prefix=None, order_by=None):
         from django.db.models.fields.related import RelatedObject
         if instance is None:
             self.instance = self.model()
@@ -472 +472 @@
         # is there a better way to get the object descriptor?
         self.rel_name = RelatedObject(self.fk.rel.to, self.model, self.fk).get_accessor_name()
         qs = self.model._default_manager.filter(**{self.fk.name: self.instance})
+        if order_by:
+            qs = qs.order_by(order_by)
         super(BaseInlineFormSet, self).__init__(data, files, prefix=prefix or self.rel_name,
                                                 queryset=qs)
 
@@ -543 +545 @@
 
 def inlineformset_factory(parent_model, model, form=ModelForm,
                           formset=BaseInlineFormSet, fk_name=None,
-                          fields=None, exclude=None,
+                          fields=None, exclude=None, order_by=None,
                           extra=3, can_order=False, can_delete=True, max_num=0,
                           formfield_callback=lambda f: f.formfield()):
     """
@@ -551 +553 @@
 
     You must provide ``fk_name`` if ``model`` has more than one ``ForeignKey``
     to ``parent_model``.
+
+    Optional parameter order_by chains an order_by filter to the resulting
+    ``InlineFormSet`` queryset. This avoids some unpleasant reordering effects when using
+    PRG (Post/Redirect/Get) with some database engines. Example: order_by='-pub_date'
+
     """
     fk = _get_foreign_key(parent_model, model, fk_name=fk_name)
     # enforce a max_num=1 when the foreign key to the parent model is unique.
@@ -573 +580 @@
         'fields': fields,
         'exclude': exclude,
         'max_num': max_num,
+        'order_by': order_by,
     }
     FormSet = modelformset_factory(model, **kwargs)
     FormSet.fk = fk