django自定義命令抱怨AssertionError：ForeignKey（None）無效。爲什麼

Question

我跟着django自定義命令教程，鏈接是here。

我的工作目錄是這樣的：

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

我的代碼如下所示：

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

class Command(BaseCommand): 

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

當我運行命令manage.py my_command，我得到了以下錯誤，

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' 

顯然，ForeignKey的第一個參數是我的模型單位，我該如何沉默編譯器的comp laint？

ps：我的模型看起來像這樣： 我的模型現在看起來像這樣。

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：用戶外鍵不作任何麻煩，而單元不...

2：我的網絡服務器可以運行沒有任何問題，而命令行無法運行...

Answer 1

您的班級Units應該在您的班級之前Salarys：

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) 

還有一個建議：這是以單數命名模型的最佳實踐。 Django會自動「複製」它們。如果Django的無法正常複數化類的名稱，你可以通過添加以下的機型元指定自己複數：

class Meta: 
    verbose_name_plural = "salaries"