Thanks a lot for your help Malcom.
Malcolm Tredinnick escribió, El 18/08/2008 0:03:
>
> On Sun, 2008-08-17 at 23:51 +0200, MarC wrote:
>> Hi again,
>> I'm still fighting against it and reading related posts in the mailing list
>> archive with no
>> success... Now I just found it won't work either for a simpler example.
>> Looks like I should be doing something really stupid but I can't see it...
>>
>> from django.db import models
>>
>> class Test2(models.Model):
>> name = models.CharField(max_length=50);
>> def __unicode__(self):
>> return self.name
>>
>> class Test(models.Model):
>> name = models.CharField(max_length=50);
>> rel = models.ForeignKey(Test2);
>
>> def __unicode__(self):
>> return self.name
>>
>> SHELL:
>> >>> from trustworker.main.models import *
>> >>> t2=Test2(name="sample");
>> >>> t=Test(name="example",rel=t2);
>> >>> t2.save();
>> >>> t.save();
>
> This is caused by an implementation detail, but the basic rule is "don't
> use unsaved objects as related objects".
>
> What's going on is when you do the "rel=t2" part, the related field
> attribute actually extracts the value it will be storing (the primary
> key value of t2, in this case) and stores that. It doesn't store the
> reference to t2 directly on the attribute (it does store the reference
> internally for caching reasons, but that's beside the point here).
>
> Since t2 is unsaved, it's primary key attribute is None and that's why
> the wheels fall off later. Saving t2 prior to using it to construct t
> will almost certainly fix the problem.
>
> Yes, this is slightly odd and a little trappy.
>
> Regards,
> Malcolm
>
>
>
> >
>
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