How to make django association reference to itself - django

Question

I have:
class Direction(models.Model):
left = models.OneToOneField(
'self', on_delete=models.SET_NULL, null=True, related_name='right')
right = models.OneToOneField(
'self', on_delete=models.SET_NULL, null=True, related_name='left')
The error:
ant.Direction.left: (fields.E302) Reverse accessor for 'ant.Direction.left' clashes with field name 'ant.Direction.right'.
HINT: Rename field 'ant.Direction.right', or add/change a related_name argument to the definition for field 'ant.Direction.left'.
How does one make this relationship so that a.left = b and b.right = a?

Answer 1

You can not use as related_name the same as the fields that have been defined. You likely do not want to work with two OneToOneFields anyway, you can define a single OneToOneField, and set the related name to the opposite, so:
class Direction(models.Model):
left = models.OneToOneField(
'self',
on_delete=models.SET_NULL,
null=True,
related_name='right'
)
# no right
So now if a direction a has as .left a direction b, then b has as .right the object a.
If there is no .right, then accessing .right will raise a Direction.DoesNotExist exception, we can however fix this issue by making use of another for the related_name, and work with a property that will wrap it in a try-except:
class Direction(models.Model):
left = models.OneToOneField(
'self',
on_delete=models.SET_NULL,
null=True,
related_name='_right'
)
#property
def right(self):
try:
return self._right
except Direction.DoesNotExist:
return None
#right.setter
def _set_right(self, value):
self._right = value