Question

我已经按照django自定义命令教程，链接是here。

我的工作目录如下所示：

myapps/
    __init__.py
    models.py
    management/  
        __init__.py
        commands/
            __init__.py
            my_command.py
    tests.py
    views.py

我的代码如下所示：

from django.core.management.base import BaseCommand, CommandError

class Command(BaseCommand):

    def handle(self, *args, **options):
        print '=========='
        self.stdout.write('Successfully closed poll ttt')

当我运行命令manage.py my_command时，我收到以下错误，

  File "D:/ERP\apps\person\salary\models.py", line 8, in <module>
    class Salarys(models.Model):
  File "D:/ERP\apps\person\salary\models.py", line 14, in Salarys
    Unit = models.ForeignKey(Units, verbose_name = u'def_unit, on_delete = models.PROTECT) 
  File "D:\Python27\Lib\site-packages\django\db\models\fields\related.py", line 910, in __init__
    assert isinstance(to, basestring), "%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'

显然，ForeignKey的第一个参数是我的模型单位，如何使编译器的投诉无声？

ps：我的模型看起来像这样：我的模型现在看起来像这样。

class Salarys(models.Model):
    '''
    describe : salary table
    author : liyang 2013-1-23
    '''
    User = models.ForeignKey(Users, verbose_name = u'account', on_delete = models.PROTECT) 
    Unit = models.ForeignKey(Units, verbose_name = u'def_unit', on_delete = models.PROTECT, null=True) 
    yy = models.IntegerField(u'year)
    mm = models.IntegerField(u'month')
    class Meta:
        db_table = 'users_salarys'

class Units(models.Model):
    '''
    describe : def unit model
    author : liyang 2012-12-4 11:45
    '''
    name = models.CharField(u'name',max_length = 20) 
    cname = models.CharField(u'company name',max_length = 20, blank = True, null = True) 
    aname = models.CharField(u'company short cut',max_length = 20, blank = True, null = True)         
    telephone = models.CharField(u'contact',max_length = 20, blank = True, null = True)         
    website = models.CharField(u'website',max_length = 25, blank = True, null = True)         
    address = models.CharField(u'address',max_length = 50, blank = True, null = True)         
    class Meta:
        db_table = 'units'

...

奇怪的事情是

1：用户外键在单位执行时不会出现任何问题......

2：无法运行命令行时，我的Web服务器可以正常运行...

Answer 1

您的课程Units应该在课程Salarys之前：

class Units(models.Model):
    ...

class Salarys(models.Model):
    user = models.ForeignKey(Users, verbose_name = u'account', on_delete = models.PROTECT) 
    unit = models.ForeignKey(Units, verbose_name = u'def_unit', on_delete = models.PROTECT, null=True)

还有一个建议：以单数形式命名模型是最佳做法。 Django会自动“复数”它们。如果Django无法正确复数类名，您可以通过将以下内容添加到模型Meta来指定自己的复数：

class Meta:
    verbose_name_plural = "salaries"

django custom命令抱怨AssertionError：ForeignKey（None）无效。为什么

1 个答案: