嗯,出于某种原因,即使在最简单的模型上,我似乎也无法让 F 正常工作。这里是 Django 1.9.x。
最简单的形式是 TestAccount
class TestAccount(models.Model):
decimal = models.DecimalField(max_digits=5, decimal_places=2)
integer = models.IntegerField()
In [1]: ta = TestAccount()
In [2]: ta.integer = 1
In [3]: ta.decimal = 1
In [4]: ta.save()
In [5]:
In [5]:
In [5]: ta
Out[5]: <TestAccount: TestAccount object>
In [6]: ta.id
Out[6]: 1L
In [7]: from django.db.models.expressions import F
In [8]: ta = TestAccount.objects.get(id=1)
In [9]: ta.integer = F('integer') + 1
In [10]: ta.save()
---------------------------------------------------------------------------
ValidationError Traceback (most recent call last)
<ipython-input-10-6e9eda341b34> in <module>()
----> 1 ta.save()
/usr/lib/python2.7/site-packages/django/db/models/base.pyc in save(self, force_insert, force_update, using, update_fields)
706
707 self.save_base(using=using, force_insert=force_insert,
--> 708 force_update=force_update, update_fields=update_fields)
709 save.alters_data = True
710
/usr/lib/python2.7/site-packages/django/db/models/base.pyc in save_base(self, raw, force_insert, force_update, using, update_fields)
730 if not meta.auto_created:
731 signals.pre_save.send(sender=origin, instance=self, raw=raw, using=using,
--> 732 update_fields=update_fields)
733 with transaction.atomic(using=using, savepoint=False):
734 if not raw:
/usr/lib/python2.7/site-packages/django/dispatch/dispatcher.pyc in send(self, sender, **named)
190
191 for receiver in self._live_receivers(sender):
--> 192 response = receiver(signal=self, sender=sender, **named)
193 responses.append((receiver, response))
194 return responses
/media/sf_helium/build/helium/internal/signals.pyc in validate_model(sender, **kwargs)
12 def validate_model(sender, **kwargs):
13 if 'raw' in kwargs and not kwargs['raw']:
---> 14 kwargs['instance'].full_clean()
15
16 @receiver(pre_delete)
/usr/lib/python2.7/site-packages/django/db/models/base.pyc in full_clean(self, exclude, validate_unique)
1142
1143 if errors:
-> 1144 raise ValidationError(errors)
1145
1146 def clean_fields(self, exclude=None):
ValidationError: {'integer': [u"'F(integer) + Value(1)' value must be an integer."]}
但根据这个:https://docs.djangoproject.com/en/1.9/ref/models/instances/#updating-attributes-based-on-existing-fields https://docs.djangoproject.com/en/1.9/ref/models/instances/#updating-attributes-based-on-existing-fields它应该有效...
我不知道为什么 F 没有被排除在验证之外。应该是这样,Django 应该只创建一个查询来更新它。