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Fixed #10981 -- Clarified documentation regarding lazy cross-application relationships. Thanks to Ramiro for the suggestion.

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git-svn-id: http://code.djangoproject.com/svn/django/trunk@10971 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Russell Keith-Magee 2009-06-10 12:45:29 +00:00
parent 74131e82eb
commit 6c36d4c4f8
1 changed files with 20 additions and 10 deletions
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30
docs/ref/models/fields.txt
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@ -800,21 +800,22 @@ you can use the name of the model, rather than the model object itself::
class Manufacturer(models.Model):
# ...
Note, however, that this only refers to models in the same ``models.py`` file --
you cannot use a string to reference a model defined in another application or
imported from elsewhere.
.. versionadded:: 1.0
.. versionchanged:: 1.0
Refering models in other applications must include the application label.
To refer to models defined in another
application, you must instead explicitly specify the application label. For
example, if the ``Manufacturer`` model above is defined in another application
called ``production``, you'd need to use::
To refer to models defined in another application, you can explicitly specify
a model with the full application label. For example, if the ``Manufacturer``
model above is defined in another application called ``production``, you'd
need to use::
class Car(models.Model):
manufacturer = models.ForeignKey('production.Manufacturer')
This sort of reference can be useful when resolving circular import
dependencies between two applications.
Database Representation
~~~~~~~~~~~~~~~~~~~~~~~
Behind the scenes, Django appends ``"_id"`` to the field name to create its
database column name. In the above example, the database table for the ``Car``
model will have a ``manufacturer_id`` column. (You can change this explicitly by
@ -824,6 +825,9 @@ deal with the field names of your model object.
.. _foreign-key-arguments:
Arguments
~~~~~~~~~
:class:`ForeignKey` accepts an extra set of arguments -- all optional -- that
define the details of how the relation works.
@ -871,6 +875,9 @@ the model is related. This works exactly the same as it does for
:class:`ForeignKey`, including all the options regarding :ref:`recursive
<recursive-relationships>` and :ref:`lazy <lazy-relationships>` relationships.
Database Representation
~~~~~~~~~~~~~~~~~~~~~~~
Behind the scenes, Django creates an intermediary join table to represent the
many-to-many relationship. By default, this table name is generated using the
names of the two tables being joined. Since some databases don't support table
@ -882,6 +889,9 @@ You can manually provide the name of the join table using the
.. _manytomany-arguments:
Arguments
~~~~~~~~~
:class:`ManyToManyField` accepts an extra set of arguments -- all optional --
that control how the relationship functions.