1

我有两个相互导入的类：

配置文件/models.py

class Company(models.Model):
    name = ...

class CompanyReview(models.Model):
    company = models.ForeignKey(Company)
    from action.models import CompanyAction
    action = models.ForeignKey(CompanyAction)

动作/models.py

from profile.models import Company
class CompanyAction(models.Model):
    company = models.ForeignKey(Company, null = True, blank = True)

当在服务器上执行 Django 应用程序或在 shell 中调用视图函数时，循环导入有效。但是，当我导入其中一个类时，Django 命令将失败并出现错误（请参阅下面的 Traceback）。

为什么会出现这种情况并且只会在 中引起问题command method？我怎样才能避免错误？我尝试过延迟导入CompanyAction该类，但它导致了相同的错误消息。

不工作的替代方案：

class CompanyReview(models.Model):
    company = models.ForeignKey(Company)
    from django.db.models import get_model
    _model = get_model('action', 'CompanyAction')
    action = models.ForeignKey(_model)

有趣的是，如果我执行命令函数并且导入了类，则该变量_model为空。当我加载./manage.py shell时，变量包含正确的类名。为什么会这样？

追溯

(virtual-env)PC:neurix$ python manage.py close_action
Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/Development/virtual-re/lib/python2.7/site-packages/django/core/management/__init__.py", line 453, in execute_from_command_line
    utility.execute()
  File "/Users/Development/virtual-re/lib/python2.7/site-packages/django/core/management/__init__.py", line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/Development/virtual-re/lib/python2.7/site-packages/django/core/management/__init__.py", line 272, in fetch_command
    klass = load_command_class(app_name, subcommand)
  File "/Users/Development/virtual-re/lib/python2.7/site-packages/django/core/management/__init__.py", line 77, in load_command_class
    module = import_module('%s.management.commands.%s' % (app_name, name))
  File "/Users/Development/virtual-re/lib/python2.7/site-packages/django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/Users/Development/project/apps/action/management/commands/close_action.py", line 2, in <module>
    from action.models import CompanyAction
  File "/Users/Development/project/apps/action/models.py", line 26, in <module>
    from profile.models import Company
  File "/Users/Development/apps/profile/models.py", line 436, in <module>
    class CompanyReview(models.Model):
  File "/Users/Development/project/apps/profile/models.py", line 446, in CompanyReview
    action = models.ForeignKey(_model)
  File "/Users/Development/virtual-re/lib/python2.7/site-packages/django/db/models/fields/related.py", line 993, in __init__
    assert isinstance(to, six.string_types), "%s(%r) is invalid. First parameter to ForeignKey must be either a model, a model name, or the string %r" % (self.__class__.__name__, to, RECURSIVE_RELATIONSHIP_CONSTANT)
AssertionError: ForeignKey(None) is invalid. First parameter to ForeignKey must be either a model, a model name, or the string 'self'
4

1 回答 1

1

Django 有一个用于停止外键循环导入的系统，详见此处：https ://docs.djangoproject.com/en/dev/ref/models/fields/#foreignkey

你会想做这样的事情：

class CompanyReview(models.Model):
    company = models.ForeignKey(Company)
    action = models.ForeignKey('action.CompanyAction')

class CompanyAction(models.Model):
    company = models.ForeignKey('profile.Company', null = True, blank = True)
于 2013-05-11T17:29:50.520 回答