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from django.contrib.contenttypes.models import ContentType
from django.db import DEFAULT_DB_ALIAS
from polymorphic.base import PolymorphicModelBase
from polymorphic.models import PolymorphicModel
def reset_polymorphic_ctype(*models, **filters):
"""
Set the polymorphic content-type ID field to the proper model
Sort the ``*models`` from base class to descending class,
to make sure the content types are properly assigned.
Add ``ignore_existing=True`` to skip models which already
have a polymorphic content type.
"""
using = filters.pop("using", DEFAULT_DB_ALIAS)
ignore_existing = filters.pop("ignore_existing", False)
models = sort_by_subclass(*models)
if ignore_existing:
# When excluding models, make sure we don't ignore the models we
# just assigned the an content type to. hence, start with child first.
models = reversed(models)
for new_model in models:
new_ct = ContentType.objects.db_manager(using).get_for_model(
new_model, for_concrete_model=False
)
qs = new_model.objects.db_manager(using)
if ignore_existing:
qs = qs.filter(polymorphic_ctype__isnull=True)
if filters:
qs = qs.filter(**filters)
qs.update(polymorphic_ctype=new_ct)
def _compare_mro(cls1, cls2):
if cls1 is cls2:
return 0
try:
index1 = cls1.mro().index(cls2)
except ValueError:
return -1 # cls2 not inherited by 1
try:
index2 = cls2.mro().index(cls1)
except ValueError:
return 1 # cls1 not inherited by 2
return (index1 > index2) - (index1 < index2) # python 3 compatible cmp.
def sort_by_subclass(*classes):
"""
Sort a series of models by their inheritance order.
"""
from functools import cmp_to_key
return sorted(classes, key=cmp_to_key(_compare_mro))
def get_base_polymorphic_model(ChildModel, allow_abstract=False):
"""
First the first concrete model in the inheritance chain that inherited from the PolymorphicModel.
"""
for Model in reversed(ChildModel.mro()):
if (
isinstance(Model, PolymorphicModelBase)
and Model is not PolymorphicModel
and (allow_abstract or not Model._meta.abstract)
):
return Model
return None
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