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| author | Denis <theoden-dd@users.noreply.github.com> | 2018-03-21 02:43:33 +0200 |
|---|---|---|
| committer | Tim Graham <timograham@gmail.com> | 2018-03-20 20:43:33 -0400 |
| commit | 1834490a0c45a87b718c9ee84523a6d7ec6c15ee (patch) | |
| tree | 8ab3e1e5438f66611a77f2f7c58b4f77bc4aad27 /docs | |
| parent | 27ca5ce19f5f184018a61611c1bc319113b1d107 (diff) | |
| download | django-1834490a0c45a87b718c9ee84523a6d7ec6c15ee.tar.gz | |
Refs #11278 -- Clarified RelatedManager differences between reverse one-to-many and many-to-many relations.
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/topics/db/queries.txt | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/docs/topics/db/queries.txt b/docs/topics/db/queries.txt index efbc7c569b..01bb0de7da 100644 --- a/docs/topics/db/queries.txt +++ b/docs/topics/db/queries.txt @@ -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 ------------------------ |