#7623: Multi-table inheritance does not allow linking new instance of child
model
to existing parent model instance.
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Reporter: [EMAIL PROTECTED] | Owner: nobody
Status: new | Milestone:
Component: Core framework | Version: SVN
Resolution: | Keywords:
model-inheritance, multi-table-inheritance
Stage: Unreviewed | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by korpios):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Comment:
I have a Bazaar branch available that solves this issue:
https://code.launchpad.net/~theonion/django/makechild
In short, it adds a couple of new methods to `QuerySet` / `Manager`:
`prepare_child()` and `create_child()`. For an existing `Place` `p` that
isn't currently a `Restaurant`, you could do either of the following:
{{{
# p is an existing Place
r = Restaurant.objects.prepare_child(p)
r.cusine = "Sushi"
r.rating = 5
r.save()
# or, alternately
r = Restaurant.objects.create_child(p, cusine="Sushi", rating=5)
}}}
While `create_child()` saves to the database, `prepare_child()` does not;
the latter allows you to further alter the instance before saving.
I tried several alternate routes — supporting setting children directly
from parents, supporting setting parents directly from children, a single
unified `child()` method — and none worked cleanly. The unified `child()`
method presented the issue of passing a `save` flag; there was no way to
avoid a collision with a field named `save` in the keyword arguments.
I'll add an initial patch here based on the Bazaar repository for now; I
still need to add tests. Any patches here will lag behind the Bazaar
repository, as the latter is where my actual development takes place.
--
Ticket URL: <http://code.djangoproject.com/ticket/7623#comment:1>
Django Code <http://code.djangoproject.com/>
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