执行迁移时，外键生成 'NoneType' 对象没有属性“_meta”

Question

我有三个不同的应用程序：

人，从用户扩展
公司，从用户扩展而来
Candidate，继承自 Person

在人模块中：

class Person(User):
    introductory_text = models.TextField(verbose_name=_(u"Introductory text"), blank=True, null=True)
    image = FilerImageField(null=True, blank=True, verbose_name="Image", related_name='image_person')

    class Meta:
        verbose_name = _(u"Person")
        verbose_name_plural = _(u"People")

    def __str__(self):
        return str(self.email)

在组织中，非常相似的人：

class Organization(User):
    organization_name = models.CharField(verbose_name=_(u"Organiztion name"), max_length=40)
    CIF = models.CharField(verbose_name=_("CIF"), max_length=9)

    class Meta:
        verbose_name=_(u"Organization")
        verbose_name_plural=_(u"Organizations")

    def __str__(self):
        return str(self.organization_name)

最后，在 候选人 应用中：

class Profile(models.Model):
    person = models.OneToOneField('person.Person', related_name='profile_person')
    mute_offer = models.BooleanField(verbose_name=_(u"Mute offers?"))

    class Meta:
        verbose_name = _(u"Profile")
        verbose_name_plural = _(u"Profiles")

    def __str__(self):
        return "Profile"

当我进行 makemigrations 时，一切正常，但是在进行迁移时：

    Operations to perform:
  Synchronize unmigrated apps: staticfiles, modeltranslation, redactor, messages, linkedin, bootstrap_admin, allauth, facebook, google
  Apply all migrations: person, auth, sites, easy_thumbnails, admin, contenttypes, django_messages, filer, notifications, sessions, push_notifications, organization, account, candidate, socialaccount
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states...Traceback (most recent call last):
  File "./manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/core/management/__init__.py", line 330, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/core/management/base.py", line 390, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/core/management/base.py", line 441, in execute
    output = self.handle(*args, **options)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/core/management/commands/migrate.py", line 221, in handle
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/db/migrations/executor.py", line 104, in migrate
    state = migration.mutate_state(state, preserve=do_run)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/db/migrations/migration.py", line 83, in mutate_state
    operation.state_forwards(self.app_label, new_state)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/db/migrations/operations/fields.py", line 51, in state_forwards
    state.reload_model(app_label, self.model_name_lower)
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/db/migrations/state.py", line 122, in reload_model
    related_models.update(get_related_models_recursive(rel_model))
  File "/home/karlie/.virtualenvs/tuwing/lib/python3.4/site-packages/django/db/migrations/state.py", line 57, in get_related_models_recursive
    rel_app_label, rel_model_name = rel_mod._meta.app_label, rel_mod._meta.model_name
AttributeError: 'NoneType' object has no attribute '_meta'

如果我删除字段 person OneToOneField 一切正常，所以我想这可能是因为我正在与从 User 扩展的 Person 建立关系。我怎样才能解决这个问题？我无法更改应用程序的结构，如果因为我有两个从 Django 的用户模型扩展的模型，我认为用用户做 onetoonefield 不是一个好主意，因为它只影响人.

任何帮助将不胜感激，

谢谢！

Answer 1

这可能只是一个依赖性问题。

 Apply all migrations: person, auth, ..., organization, account, candidate, ...

您的要求如下： candidate.Profile 需要 person.Person 而 person.Person 需要 auth.User

您不需要运行再次进行迁移 auth.User。所以请执行以下操作：

./manage.py makemigrations profile
./manage.py makemigrations person
./manage.py makemigrations organization
./manage.py migrate

Answer 2

我已经解决了导入应用程序模块的问题，如下所示：

from person import models as person_class

然后，在 OneToOneField 的字段中：

person = models.OneToOneField(person_class.Person, verbose_name=_(u"Person"), related_name="person")

编辑:
错了，错误又出来了。搜索累了，我已经将项目更改为Django 1.7（之前是django 1.8）并且没有再次出现此错误。

执行迁移时，外键生成 'NoneType' 对象没有属性“_meta”

ForeignKey produces 'NoneType' object has no attribute '_meta' when doing a migrate

django

django-models

models