Permalink
Browse files

Fixed #5390 -- Added signals for m2m operations. Thanks to the many p…

…eople (including, most recently, rvdrijst and frans) that have contributed to this patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12223 bcc190cf-cafb-0310-a4f2-bffc1f526a37
  • Loading branch information...
1 parent f56f6e9 commit 6afd505b5be528bc5728bc9b9acd48276be457b4 @freakboy3742 freakboy3742 committed Jan 13, 2010
@@ -427,7 +427,8 @@ def create_many_related_manager(superclass, rel=False):
through = rel.through
class ManyRelatedManager(superclass):
def __init__(self, model=None, core_filters=None, instance=None, symmetrical=None,
- join_table=None, source_field_name=None, target_field_name=None):
+ join_table=None, source_field_name=None, target_field_name=None,
+ reverse=False):
super(ManyRelatedManager, self).__init__()
self.core_filters = core_filters
self.model = model
@@ -437,6 +438,7 @@ def __init__(self, model=None, core_filters=None, instance=None, symmetrical=Non
self.target_field_name = target_field_name
self.through = through
self._pk_val = self.instance.pk
+ self.reverse = reverse
if self._pk_val is None:
raise ValueError("%r instance needs to have a primary key value before a many-to-many relationship can be used." % instance.__class__.__name__)
@@ -516,14 +518,19 @@ def _add_items(self, source_field_name, target_field_name, *objs):
source_field_name: self._pk_val,
'%s__in' % target_field_name: new_ids,
})
- vals = set(vals)
-
+ new_ids = new_ids - set(vals)
# Add the ones that aren't there already
- for obj_id in (new_ids - vals):
+ for obj_id in new_ids:
self.through._default_manager.using(self.instance._state.db).create(**{
'%s_id' % source_field_name: self._pk_val,
'%s_id' % target_field_name: obj_id,
})
+ if self.reverse or source_field_name == self.source_field_name:
+ # Don't send the signal when we are inserting the
+ # duplicate data row for symmetrical reverse entries.
+ signals.m2m_changed.send(sender=rel.through, action='add',
+ instance=self.instance, reverse=self.reverse,
+ model=self.model, pk_set=new_ids)
def _remove_items(self, source_field_name, target_field_name, *objs):
# source_col_name: the PK colname in join_table for the source object
@@ -544,9 +551,21 @@ def _remove_items(self, source_field_name, target_field_name, *objs):
source_field_name: self._pk_val,
'%s__in' % target_field_name: old_ids
}).delete()
+ if self.reverse or source_field_name == self.source_field_name:
+ # Don't send the signal when we are deleting the
+ # duplicate data row for symmetrical reverse entries.
+ signals.m2m_changed.send(sender=rel.through, action="remove",
+ instance=self.instance, reverse=self.reverse,
+ model=self.model, pk_set=old_ids)
def _clear_items(self, source_field_name):
# source_col_name: the PK colname in join_table for the source object
+ if self.reverse or source_field_name == self.source_field_name:
+ # Don't send the signal when we are clearing the
+ # duplicate data rows for symmetrical reverse entries.
+ signals.m2m_changed.send(sender=rel.through, action="clear",
+ instance=self.instance, reverse=self.reverse,
+ model=self.model, pk_set=None)
self.through._default_manager.using(self.instance._state.db).filter(**{
source_field_name: self._pk_val
}).delete()
@@ -579,7 +598,8 @@ def __get__(self, instance, instance_type=None):
instance=instance,
symmetrical=False,
source_field_name=self.related.field.m2m_reverse_field_name(),
- target_field_name=self.related.field.m2m_field_name()
+ target_field_name=self.related.field.m2m_field_name(),
+ reverse=True
)
return manager
@@ -596,6 +616,7 @@ def __set__(self, instance, value):
manager.clear()
manager.add(*value)
+
class ReverseManyRelatedObjectsDescriptor(object):
# This class provides the functionality that makes the related-object
# managers available as attributes on a model class, for fields that have
@@ -629,7 +650,8 @@ def __get__(self, instance, instance_type=None):
instance=instance,
symmetrical=(self.field.rel.symmetrical and isinstance(instance, rel_model)),
source_field_name=self.field.m2m_field_name(),
- target_field_name=self.field.m2m_reverse_field_name()
+ target_field_name=self.field.m2m_reverse_field_name(),
+ reverse=False
)
return manager
@@ -12,3 +12,5 @@
post_delete = Signal(providing_args=["instance"])
post_syncdb = Signal(providing_args=["class", "app", "created_models", "verbosity", "interactive"])
+
+m2m_changed = Signal(providing_args=["action", "instance", "reverse", "model", "pk_set"])
View
@@ -170,6 +170,123 @@ Arguments sent with this signal:
Note that the object will no longer be in the database, so be very
careful what you do with this instance.
+m2m_changed
+-----------
+
+.. data:: django.db.models.signals.m2m_changed
+ :module:
+
+Sent when a :class:`ManyToManyField` is changed on a model instance.
+Strictly speaking, this is not a model signal since it is sent by the
+:class:`ManyToManyField`, but since it complements the
+:data:`pre_save`/:data:`post_save` and :data:`pre_delete`/:data:`post_delete`
+when it comes to tracking changes to models, it is included here.
+
+Arguments sent with this signal:
+
+ ``sender``
+ The intermediate model class describing the :class:`ManyToManyField`.
+ This class is automatically created when a many-to-many field is
+ defined; it you can access it using the ``through`` attribute on the
+ many-to-many field.
+
+ ``instance``
+ The instance whose many-to-many relation is updated. This can be an
+ instance of the ``sender``, or of the class the :class:`ManyToManyField`
+ is related to.
+
+ ``action``
+ A string indicating the type of update that is done on the relation.
+ This can be one of the following:
+
+ ``"add"``
+ Sent *after* one or more objects are added to the relation
+ ``"remove"``
+ Sent *after* one or more objects are removed from the relation
+ ``"clear"``
+ Sent *before* the relation is cleared
+
+ ``reverse``
+ Indicates which side of the relation is updated (i.e., if it is the
+ forward or reverse relation that is being modified).
+
+ ``model``
+ The class of the objects that are added to, removed from or cleared
+ from the relation.
+
+ ``pk_set``
+ With the ``"add"`` and ``"remove"`` action, this is a list of
+ primary key values that have been added to or removed from the relation.
+
+ For the ``"clear"`` action, this is ``None``.
+
+For example, if a ``Pizza`` can have multiple ``Topping`` objects, modeled
+like this:
+
+.. code-block:: python
+
+ class Topping(models.Model):
+ # ...
+
+ class Pizza(models.Model):
+ # ...
+ toppings = models.ManyToManyField(Topping)
+
+If we would do something like this:
+
+.. code-block:: python
+
+ >>> p = Pizza.object.create(...)
+ >>> t = Topping.objects.create(...)
+ >>> p.toppings.add(t)
+
+the arguments sent to a :data:`m2m_changed` handler would be:
+
+ ============== ============================================================
+ Argument Value
+ ============== ============================================================
+ ``sender`` ``Pizza.toppings.through`` (the intermediate m2m class)
+
+ ``instance`` ``p`` (the ``Pizza`` instance being modified)
+
+ ``action`` ``"add"``
+
+ ``reverse`` ``False`` (``Pizza`` contains the :class:`ManyToManyField`,
+ so this call modifies the forward relation)
+
+ ``model`` ``Topping`` (the class of the objects added to the
+ ``Pizza``)
+
+ ``pk_set`` ``[t.id]`` (since only ``Topping t`` was added to the relation)
+ ============== ============================================================
+
+And if we would then do something like this:
+
+.. code-block:: python
+
+ >>> t.pizza_set.remove(p)
+
+the arguments sent to a :data:`m2m_changed` handler would be:
+
+ ============== ============================================================
+ Argument Value
+ ============== ============================================================
+ ``sender`` ``Pizza.toppings.through`` (the intermediate m2m class)
+
+ ``instance`` ``t`` (the ``Topping`` instance being modified)
+
+ ``action`` ``"remove"``
+
+ ``reverse`` ``True`` (``Pizza`` contains the :class:`ManyToManyField`,
+ so this call modifies the reverse relation)
+
+ ``model`` ``Pizza`` (the class of the objects removed from the
+ ``Topping``)
+
+ ``pk_set`` ``[p.id]`` (since only ``Pizza p`` was removed from the
+ relation)
+ ============== ============================================================
+
class_prepared
--------------
@@ -29,6 +29,9 @@ notifications:
Sent before or after a model's :meth:`~django.db.models.Model.delete`
method is called.
+ * :data:`django.db.models.signals.m2m_changed`
+
+ Sent when a :class:`ManyToManyField` on a model is changed.
* :data:`django.core.signals.request_started` &
:data:`django.core.signals.request_finished`
@@ -0,0 +1 @@
+
Oops, something went wrong.

0 comments on commit 6afd505

Please sign in to comment.