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from functools import partial
from django.db import models
from django.db.models.fields.related import (
RECURSIVE_RELATIONSHIP_CONSTANT, ManyToManyDescriptor, RelatedField,
create_many_to_many_intermediary_model,
)
class CustomManyToManyField(RelatedField):
"""
Ticket #24104 - Need to have a custom ManyToManyField,
which is not an inheritor of ManyToManyField.
"""
many_to_many = True
def __init__(self, to, db_constraint=True, swappable=True, related_name=None, related_query_name=None,
limit_choices_to=None, symmetrical=None, through=None, through_fields=None, db_table=None, **kwargs):
try:
to._meta
except AttributeError:
to = str(to)
kwargs['rel'] = models.ManyToManyRel(
self, to,
related_name=related_name,
related_query_name=related_query_name,
limit_choices_to=limit_choices_to,
symmetrical=symmetrical if symmetrical is not None else (to == RECURSIVE_RELATIONSHIP_CONSTANT),
through=through,
through_fields=through_fields,
db_constraint=db_constraint,
)
self.swappable = swappable
self.db_table = db_table
if kwargs['rel'].through is not None and self.db_table is not None:
raise ValueError(
'Cannot specify a db_table if an intermediary model is used.'
)
super().__init__(
related_name=related_name,
related_query_name=related_query_name,
limit_choices_to=limit_choices_to,
**kwargs,
)
def contribute_to_class(self, cls, name, **kwargs):
if self.remote_field.symmetrical and (
self.remote_field.model == "self" or self.remote_field.model == cls._meta.object_name):
self.remote_field.related_name = "%s_rel_+" % name
super().contribute_to_class(cls, name, **kwargs)
if not self.remote_field.through and not cls._meta.abstract and not cls._meta.swapped:
self.remote_field.through = create_many_to_many_intermediary_model(self, cls)
setattr(cls, self.name, ManyToManyDescriptor(self.remote_field))
self.m2m_db_table = partial(self._get_m2m_db_table, cls._meta)
def get_internal_type(self):
return 'ManyToManyField'
# Copy those methods from ManyToManyField because they don't call super() internally
contribute_to_related_class = models.ManyToManyField.__dict__['contribute_to_related_class']
_get_m2m_attr = models.ManyToManyField.__dict__['_get_m2m_attr']
_get_m2m_reverse_attr = models.ManyToManyField.__dict__['_get_m2m_reverse_attr']
_get_m2m_db_table = models.ManyToManyField.__dict__['_get_m2m_db_table']
class InheritedManyToManyField(models.ManyToManyField):
pass
class MediumBlobField(models.BinaryField):
"""
A MySQL BinaryField that uses a different blob size.
"""
def db_type(self, connection):
return 'MEDIUMBLOB'
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