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from django.core.exceptions import ValidationError
from django.db import models
from django.utils.translation import gettext_lazy as _
from tree_queries.fields import TreeNodeForeignKey
from tree_queries.query import TreeQuerySet
class TreeNode(models.Model):
parent = TreeNodeForeignKey(
"self",
blank=True,
null=True,
on_delete=models.CASCADE,
verbose_name=_("parent"),
related_name="children",
)
objects = TreeQuerySet.as_manager()
class Meta:
abstract = True
def ancestors(self, **kwargs):
"""
Returns all ancestors of the current node
See ``TreeQuerySet.ancestors`` for details and optional arguments.
"""
return self.__class__._default_manager.ancestors(self, **kwargs)
def descendants(self, **kwargs):
"""
Returns all descendants of the current node
See ``TreeQuerySet.descendants`` for details and optional arguments.
"""
return self.__class__._default_manager.descendants(self, **kwargs)
def clean(self):
"""
Raises a validation error if saving this instance would result in loops
in the tree structure
"""
super().clean()
if (
self.parent_id
and self.pk
and (
self.__class__._default_manager.ancestors(
self.parent_id, include_self=True
)
.filter(pk=self.pk)
.exists()
)
):
raise ValidationError(_("A node cannot be made a descendant of itself."))
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