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Refs #11278 -- Clarified RelatedManager differences between reverse one-to-many and many-to-many relations.

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Denis 2018-03-21 02:43:33 +02:00 • committed by Tim Graham
parent 27ca5ce19f
commit 1834490a0c
1 changed files with 13 additions and 6 deletions
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19
docs/topics/db/queries.txt
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@ -1225,14 +1225,12 @@ be found in the :doc:`related objects reference </ref/models/relations>`.
Replace the set of related objects.
To assign the members of a related set, use the ``set()`` method with an
iterable of object instances or a list of primary key values. For example::
iterable of object instances. For example, if ``e1`` and ``e2`` are ``Entry``
instances::
b = Blog.objects.get(id=1)
b.entry_set.set([e1, e2])
In this example, ``e1`` and ``e2`` can be full Entry instances, or integer
primary key values.
If the ``clear()`` method is available, any pre-existing objects will be
removed from the ``entry_set`` before all objects in the iterable (in this
case, a list) are added to the set. If the ``clear()`` method is *not*
@ -1249,9 +1247,9 @@ Many-to-many relationships
--------------------------
Both ends of a many-to-many relationship get automatic API access to the other
end. The API works just as a "backward" one-to-many relationship, above.
end. The API works similar to a "backward" one-to-many relationship, above.
The only difference is in the attribute naming: The model that defines the
One difference is in the attribute naming: The model that defines the
:class:`~django.db.models.ManyToManyField` uses the attribute name of that
field itself, whereas the "reverse" model uses the lowercased model name of the
original model, plus ``'_set'`` (just like reverse one-to-many relationships).
@ -1273,6 +1271,15 @@ if the :class:`~django.db.models.ManyToManyField` in ``Entry`` had specified
``related_name='entries'``, then each ``Author`` instance would have an
``entries`` attribute instead of ``entry_set``.
Another difference from one-to-many relationships is that in addition to model
instances, the ``add()``, ``set()``, and ``remove()`` methods on many-to-many
relationships accept primary key values. For example, if ``e1`` and ``e2`` are
``Entry`` instances, then these ``set()`` calls work identically::
a = Author.objects.get(id=5)
a.entry_set.set([e1, e2])
a.entry_set.set([e1.pk, e2.pk])
One-to-one relationships
------------------------