Re: Basic M2M Self Reference Through Question
to be able to diferentiate both follower and following you should define
at least in one of those foreigkeys a related_name argument, so you can
call back from your user.
if you try to do it without related_name django will complain, showing you
the error message and addressing you to the sollution.
2015-09-02 21:46 GMT+01:00 James Schneider :
>
> On Sep 2, 2015 9:51 AM, "jeff newburn" wrote:
> >
> > I apologize if this is basic and I am just missing something in the
> django docs. The Django ORM allows you to do a self reference through
> another table. I understand everything about this process EXCEPT how
> Django determines which of the foreign keys to use for each side of the M2M
> relationship.
> >
> > class MyUser(...):
> > connections = models.ManyToManyField('self', through=Relationship,
> symmetrical=False)
> >
> > class Relationship(...):
> > follower = models.ForeignKey(MyUser)
> > following = models.ForeignKey(MyUser)
> >
> > So in the psuedocode example above how does Django ORM know which of the
> 2 foreign key fields to connect to? Does it just assume the first field is
> the one to use? Thanks for any help on this.
> >
>
> When you have multiple references to the same model, you have to do a bit
> of extra work to tell Django how you want things to line up. I think what
> you need to do is specify the 'through_fields' on the M2M, and set
> appropriate 'related_name' arguments for the FK's.
>
>
> https://docs.djangoproject.com/en/1.8/ref/models/fields/#django.db.models.ManyToManyField.through_fields
>
> -James
>
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Re: Basic M2M Self Reference Through Question
On Sep 2, 2015 9:51 AM, "jeff newburn" wrote:
>
> I apologize if this is basic and I am just missing something in the
django docs. The Django ORM allows you to do a self reference through
another table. I understand everything about this process EXCEPT how
Django determines which of the foreign keys to use for each side of the M2M
relationship.
>
> class MyUser(...):
> connections = models.ManyToManyField('self', through=Relationship,
symmetrical=False)
>
> class Relationship(...):
> follower = models.ForeignKey(MyUser)
> following = models.ForeignKey(MyUser)
>
> So in the psuedocode example above how does Django ORM know which of the
2 foreign key fields to connect to? Does it just assume the first field is
the one to use? Thanks for any help on this.
>
When you have multiple references to the same model, you have to do a bit
of extra work to tell Django how you want things to line up. I think what
you need to do is specify the 'through_fields' on the M2M, and set
appropriate 'related_name' arguments for the FK's.
https://docs.djangoproject.com/en/1.8/ref/models/fields/#django.db.models.ManyToManyField.through_fields
-James
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Basic M2M Self Reference Through Question
I apologize if this is basic and I am just missing something in the django
docs. The Django ORM allows you to do a self reference through another
table. I understand everything about this process EXCEPT how Django
determines which of the foreign keys to use for each side of the M2M
relationship.
class MyUser(...):
connections = models.ManyToManyField('self', through=Relationship,
symmetrical=False)
class Relationship(...):
follower = models.ForeignKey(MyUser)
following = models.ForeignKey(MyUser)
So in the psuedocode example above how does Django ORM know which of the 2
foreign key fields to connect to? Does it just assume the first field is
the one to use? Thanks for any help on this.
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