Re: Symmetrical, Self-referencing ManyToManyField with Through Table

On 25/06/2020 8:29 am, Jim Shepherd wrote:
> I am unable to get a symmetrical, self-referencing ManyToManyField
> with a through table to actually be symmetrical, at least through the
> Admin interface. I am using Django 3.0 so it looks like the capability
> is supported.
>
> Models:
> class Contact(models.Model):
> last_name = models.TextField(default='', blank=True)
> connections = models.ManyToManyField('self', through='ContactConnection', symmetrical=True, blank=True)
>
> def get_connections(self):
> return ', '.join([str(p.last_name)for pin self.connections.all()])
>
>
> class ContactConnection(models.Model):
> to_contact = models.ForeignKey(Contact, related_name='contacts', on_delete=models.CASCADE, null=False)
> from_contact = models.ForeignKey(Contact, on_delete=models.CASCADE, null=False)
> comments = models.TextField(default='', blank=True)
>

Just a stab in the dark - have you tried giving from_contact a related_name?


>
> Admin:
> class ContactConnectionInline(admin.TabularInline):
> model = Contact.connections.through
> fk_name ='from_contact' extra =0
> @admin.register(Contact)
> class ContactAdmin(admin.ModelAdmin):
> ordering = ('last_name',)
> list_display = ['last_name', 'get_connections']
> inlines = (ContactConnectionInline)
> From the Admin page, when viewing a Contact, only one-direction of the
> ContactConnection relationship is shown which makes sense due to the
> fk_name='from_contact attribute fixing the direction.
> But it seems that at least the get_connections() method would get both
> sides.
>
> Is there a way either through a query or preferably an Inline to show
> the Contacts on both sides of the ContactConnection?

Another stab ... maybe you could just display the
ContactConnectionAdmin(admin.ModelAdmin) with model=ContactConnection?

I haven't advanced to 3.x so I don't know what it is capable of.


>
> Thanks,
> Jim
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