Question

进行以下测试：

贝壳：

from app.models import Campaign
from django.contrib.auth import get_user_model

user =  get_user_model().objects.get(pk=1)

link_db = Link()
link_db.link = "test"
link_db.save()

Campaign(status="Pending", domain="www.test.org", user=user, link=link_db).save()

我收到错误异常：GFK.get_content_type不可能的参数！

为什么呢？我没有看到任何错误，也不知道这意味着什么。

广告系列：

class Campaign(models.Model):
    status = models.CharField(max_length=16, choices=MESSAGE_STATUSES, default="Pending",)
    domain = models.CharField(max_length=150)
    user = models.ForeignKey(get_user_model(),  related_name='campaign', null=True,


    link = models.ForeignKey(Link,  related_name='campaign', null=True)

链接：

class Link(models.Model):
    link = models.URLField()
    hits = models.IntegerField(default=0)

    def __repr__(self):
        return "<Link (Hits %s): %s>"%(self.hits, self.link)

    def get_short_id(self):
        _id = self.id
        digits = []
        while _id > 0:
            rem = _id % 62
            digits.append(rem)
            _id /= 62
        digits.reverse()
        return index_to_char(digits)

    @staticmethod
    def decode_id(string):
        i = 0
        for c in string:
            i = i * 64 + _char_map.index(c)
        return i

完整筹码：

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/user/Documents/workspace/test/django-env/lib/python2.7/site-packages/django/db/models/base.py", line 327, in __init__
    signals.pre_init.send(sender=self.__class__, args=args, kwargs=kwargs)
  File "/Users/user/Documents/workspace/test/django-env/lib/python2.7/site-packages/django/dispatch/dispatcher.py", line 170, in send
    response = receiver(signal=self, sender=sender, **named)
  File "/Users/user/Documents/workspace/test/django-env/lib/python2.7/site-packages/django/contrib/contenttypes/generic.py", line 50, in instance_pre_init
    kwargs[self.ct_field] = self.get_content_type(obj=value)
  File "/Users/user/Documents/workspace/test/django-env/lib/python2.7/site-packages/django/contrib/contenttypes/generic.py", line 63, in get_content_type
    raise Exception("Impossible arguments to GFK.get_content_type!")
Exception: Impossible arguments to GFK.get_content_type!

Answer 1

您不能在模型定义中使用get_user_model，因为可以在设置所有模型之前对它们进行评估。相反，您应该直接引用settings.AUTH_USER_MODEL，如in the documentation所述。

Answer 2

我刚遇到同样的错误消息。是使用GenericForeignKey字段将代码库从django 1.8迁移到1.6并将实际对象传递给create函数，并期望Generic类通过以下方式查找content_type和object_id本身来自content_object，但我发现它没有。它在1.8中运行得很好，但在1.6中，您似乎必须自己提取content_type和object_id并将它们传递到create函数中。

对于模型：

class SomeObject(models.Model):
    content_type = models.ForeignKey(ContentType, null=True, blank=True, )
    object_id = models.PositiveIntegerField(null=True, blank=True)
    content_object = generic.GenericForeignKey('content_type', 'object_id')

所以在1.6

content_object = SomeOtherObject.create(first_name='Foo', last_name='bar')
SomeObject.objects.create(
    content_type=ContentType.objects.get_for_model(content_object),
    object_id=content_object.pk
)

并且在1.8

content_object = SomeOtherObject.create(first_name='Foo', last_name='bar')
SomeObject.objects.create(
    content_object=content_object
)

我尝试在pre_save和pre_init方法中解决此问题，但这会在调用它们之前发生。希望它可以帮助别人！

Django不可能的GFK.get_content_type参数

2 个答案: