How can I be able to use related_name to create a child model when the parent model is being created.
from django.db import models
from django.db.models.signals import pre_save, post_save
from django.dispatch import receiver
class Parent(models.Model):
name = models.TextField()
child = models.ForeignKey(Child, on_delete=models.SET_NULL, related_name="parent_child", null=True, blank=True)
def save(self, *args, **kwargs):
super().save()
@receiver(post_save, sender=Parent)
def post_save_receiver(sender, instance, *args, **kwargs)
if not instance.child:
instance.child.parent_child.create(name="I am a child")
class Child(models.Model):
name = models.CharField()
Currently, on save, I get a NoneType error:
'NoneType' object has no attribute 'parent_child'
You're trying to perform action on NoneType object eg. instance.child
because when you create your Parent instance you've to assing child to your Parent.child attribute so by default it will None so to assign child to your Parent class you can do like this & you don't require signals you can do this inside your save method.
class Parent(models.Model):
name = models.TextField()
child = models.ForeignKey(Child, on_delete=models.SET_NULL, related_name="parent_child", null=True, blank=True)
def save(self, *args, **kwargs):
self.child = Child.objects.create(name="I am a child")
super(Parent, self).save(*args, **kwargs)
also you're trying to access related object in wrong way if you're inside Parent you can access child directly using Parent.child & if you want to access Parent from Child then you can do like this Child.parent_child read more about backward relation
def post_save_receiver(sender, instance, *args, **kwargs)
if not instance.child:
child = Child(name='I am a child').save()
instance.child = child
instance.save()