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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. Replace the set of related objects.
To assign the members of a related set, use the ``set()`` method with an 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 = Blog.objects.get(id=1)
b.entry_set.set([e1, e2]) 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 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 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* 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 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 :class:`~django.db.models.ManyToManyField` uses the attribute name of that
field itself, whereas the "reverse" model uses the lowercased model name of the field itself, whereas the "reverse" model uses the lowercased model name of the
original model, plus ``'_set'`` (just like reverse one-to-many relationships). 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 ``related_name='entries'``, then each ``Author`` instance would have an
``entries`` attribute instead of ``entry_set``. ``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 One-to-one relationships
------------------------ ------------------------