Fixed #24325 -- Documented change in ModelForm.save() foreign key access.

This commit is contained in:
Tim Graham 2015-02-14 08:01:37 -05:00
parent 8a21d25033
commit 0af3822dc3
2 changed files with 23 additions and 0 deletions

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@ -711,6 +711,28 @@ Now, an error will be raised to prevent data loss::
...
ValueError: Cannot assign "<Author: John>": "Author" instance isn't saved in the database.
Accessing foreign keys in ``ModelForm.save()``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In older versions, you could access unsaved foreign key objects in
``ModelForm.save()`` when adding new objects. For example, given ``Book`` with
a ``ForeignKey`` to ``Author``::
class BookForm(forms.ModelForm):
def save(self, *args, **kwargs):
book = super(BookForm, self).save(*args, **kwargs)
book.title = "%s by %s" % (book.title, book.author.name)
return book
Now if the related instance hasn't been saved (for example, when adding an
author and some inlined books in the admin), accessing the foreign key
``book.author`` in the example) will raise ``RelatedObjectDoesNotExist``. This
change was necessary to avoid assigning unsaved objects to relations (as
described in the previous section).
To adapt the example above, you could replace ``book.author.name`` with
``self.cleaned_data['author'].name``.
Management commands that only accept positional arguments
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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@ -293,6 +293,7 @@ ing
ini
init
inline
inlined
inlines
inspectdb
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