Asked By – Prometheus
I have a method
has_related_object in my model that needs to check if a related object exists
class Business(base): name = models.CharField(max_length=100, blank=True, null=True) def has_related_object(self): return (self.customers is not None) and (self.car is not None) class Customer(base): name = models.CharField(max_length=100, blank=True, null=True) person = models.OneToOneField('Business', related_name="customer")
But I get the error:
RelatedObjectDoesNotExist: Business has no customer.
Now we will see solution for issue: Django check if a related object exists error: RelatedObjectDoesNotExist
This is because the ORM has to go to the database to check to see if
customer exists. Since it doesn’t exist, it raises an exception.
You’ll have to change your method to the following:
def has_related_object(self): has_customer = False try: has_customer = (self.customers is not None) except Customer.DoesNotExist: pass return has_customer and (self.car is not None)
I don’t know the situation with
self.car so I’ll leave it to you to adjust it if it needs it.
If you were doing this on a
Model that has the
OneToOneField on it, you would be able to do the following as a shortcut to avoid the database query.
def has_business(self): return self.business_id is not None