This custom model field is a variant of NullBooleanField, that stores only True and None (NULL) values. False is stored as NULL.
It's usefull for special purposes like unique/unique_together.
One small problem is here, that False is not lookuped as None.
This snippets is a response to 1830
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | from django.db.models.fields import subclassing
from django.core import exceptions
from django.conf import settings
from django.db import models
class TrueNoneField(models.NullBooleanField):
__metaclass__ = subclassing.SubfieldBase
def db_type(self):
if 'postgresql' in settings.DATABASE_ENGINE:
return "boolean CHECK (%s <> false)" % self.get_attname_column()[1]
else:
return super(TrueNoneField, self).db_type()
def to_python(self, value):
if value in (True, 1):
return True
elif value in (False, 0, None):
return None
raise exceptions.ValidationError("This value must be either True or None.")
def get_db_prep_save(self, value):
return super(TrueNoneField, self).get_db_prep_save(self.to_python(value))
|
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