actually, I understand how it works, it seems to be a bug anyway.
consider this:
from django.db import models
class Author(models.Model):
name = models.CharField(maxlength=50)
class Reference(models.Model):
"""
>>> a = Author(name='some name')
>>> a.save()
>>> r = Reference(title='some title')
>>> r.authors.add(a)
>>> r.save()
"""
id = models.CharField(maxlength=5, primary_key=True)
title = models.CharField(maxlength=50)
authors = models.ManyToManyField(Author)
I specified primary_key explicitly and it works without saving before
adding Author. but if you'll change id field to
id = models.AutoField(primary_key=True)
or to
id = models.IntegerField(primary_key=True)
it doesn't. weird isn't it? I tried both on django-0.96 and svn
version
best
Maxim Loginov
http://zeliboba.by.ru
On Sep 28, 10:02 pm, Leo <[EMAIL PROTECTED]> wrote:
> Django's beautiful abstraction of object-orientation is leading you
> astray... here's the test that will work (note the earlier added
> r.save()):
>
> from django.db import models
>
> class Author(models.Model):
> name = models.CharField(maxlength=50)
>
> class Reference(models.Model):
> """
> >>> a = Author(name='some name')
> >>> a.save()
> >>> r = Reference(title='some title')
> >>> r.save()
> >>> r.authors.add(a)
> >>> r.save()
> """
> title = models.CharField(maxlength=50)
> authors = models.ManyToManyField(Author)
>
> Why does this make it work? It actually makes sense if you know about
> what's happening under the hood in the relational model: the
> ManyToManyField is actually a separate table that contains the primary
> keys for the Author and Reference. In order to correctly save that
> separate table, we have to know the primary key for the Reference.
> But, we can't know that until after we've saved the Reference the
> first time. so the first r.save() saves the reference record itself,
> thereby assigning it's primary key. The second r.save() actually is
> only saving the ManyToManyField into its' separate table.
>
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