more than 1 foreign key - django

Question

I have the following models: http://slexy.org/view/s20T8yOiKZ
from mxutils.cms_services import generate_secid
from django.db import models
from django.contrib import admin
from django import forms
class World(models.Model):
title = models.CharField(max_length=150)
secid = models.SlugField(max_length=1000, editable=False)
elements = models.ManyToManyField("Element", related_name='elements', blank=True, null=True)
metadata = models.OneToOneField("Category_metadata", blank=True, null=True)
def save(self):
if not self.pk:
super(World, self).save()
self.secid = generate_secid(self.title, self.pk, World.objects.all())
return super(World, self).save()
def __unicode__(self):
return "%s" % self.title
class Element(models.Model):
parent = models.ForeignKey(World, related_name='element_parent')
world = models.ForeignKey(World, related_name='world', blank=True, null=True)
item = models.ForeignKey("Item", blank=True, null=True)
value = models.DecimalField(default=0, max_digits=5, decimal_places=3)
def save(self):
if self.world and self.item:
return None
elif not self.world and not self.item:
return None
else:
return super(Element, self).save()
def __unicode__(self):
if self.world:
return "%s" % self.world.title
else:
return "%s" % self.item.title
class ElementInline(admin.TabularInline):
model = Element
extra=1
class WorldAdmin(admin.ModelAdmin):
inlines = [ElementInline,]
list_display = ('title',)
ordering = ['title']
search_fields = ('title',)
When I try to click add button for worlds in admin page it shows me the following error:
class 'cms_sample.world_models.Element' has more than 1 ForeignKey to class 'cms_sample.world_models.World'.
I think it's something to do with inline.
What can it be?

Answer 1

Django doesn't know which of the two foreign keys (parent and world) is to be inlined using the ElementInline.
class ElementInline(admin.TabularInline):
model = Element
fk_name = 'parent' #or 'world', as applicable.
extra=1