Daniel and Matthias
Thanks for your help. I finally figured out I don't need any automatic
Django n:m at all! I just made my own n:m table and everything works the
way I expect. I'll really try to keep things simple from now on ...
Cheers
Mike
Mike Dewhirst wrote:
> Matthias Kestenholz wrote:
>
> <snip>
>
>> Is this your complete Membership model? Or do you have additional
>> fields there? If you've only got these two foreign keys, it might be
>> better to use a many to many field that references the same model (
>> ManyToManyField('self') )
>
> Thanks Matthias - exactly what I wanted - see below. It isn't the
> complete system but I'm just starting and want to get the beginnings
> more or less correctly working.
>
>> Plus, you should use unicode(), not str() inside __unicode__ -- str()
>> will bail if client_type or surname contains non-ASCII-chars.
>
> Thanks again ...
>
> Daniel Roseman wrote:
>> On Jul 24, 5:46 am, Mike Dewhirst <mi...@dewhirst.com.au> wrote:
>>> I'm new to Django and want to express a self-referencing design
>>> feature to link clients in the same table with each other.
>
> <snip>
>
>> You don't say what the error is. I can guess, though, and as always
>> the clue is in the error message (why do people never seem to read
>> these?)
>
> Thanks also Daniel. You are right of course - my apologies. I did read
> the message but did not have the brainspace to understand it at the
> time. Even now I'm relying on assumptions which I hope will become clear
> one day. Which leads me to another question about Django orm ...
>
> Does Django need to create all the tables itself? I have been dropping
> everything and re-syncdb-ing to try and make things happen. Can I make
> my own tables and ask Django to use them?
>
> My new models.py is as you and Matthias advised ...
> - - - - - - - -
> from django.db import models
>
> class Client(models.Model):
> """ base class for everyone/thing """
> surname = models.CharField(max_length=48, blank=False)
> client_type = models.CharField(max_length=24, blank=True)
> group = models.ManyToManyField('self',
> #db_table='foo_membership',
> blank=True)
>
> def __unicode__(self):
> return u'%s : %s' % (self.client_type, self.surname)
>
> class Membership(models.Model):
> """ cross (xr) referencing and linking clients """
> client_x = models.ForeignKey(Client, related_name='x_set')
> client_r = models.ForeignKey(Client, related_name='r_set')
> description = models.CharField(max_length=48, blank=False)
>
> def __unicode__(self):
> return u'Linked: %s - %s' % (unicode(self.client_x),
> unicode(self.client_r))
> - - - - - - - -
>
> If I reverse the position of the above two classes prior to syncdb,
> Django quite reasonably complains that Client (in Membership) does not
> exist. If I leave them in the above sequence it invents its own
> foo_client_group table for the n:m table and then creates my Membership
> table too.
>
> I have tried using db_table='foo_membership' but that causes ...
>
> File "C:\usr\bin\lib\site-packages\django\db\backends\util.py", line
> 19, in execute
> return self.cursor.execute(sql, params)
> psycopg2.ProgrammingError: relation "foo_membership" already exists
>
> I could cope with omitting my Membership table and adding a
> 'description' column to Django's 'foo_client_group' table - but then how
> do I make a class which knows about the foo_client_group table name?
>
>
> Is there a trick to it or have I (more likely) missed something obvious?
>
> Sorry to be so opaque. I'm just getting over a month of late nights.
>
> Thanks
>
> Mike
>
> <snip>
>
> >
>
>
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