从夹具加载数据时出错

Question

我有以下模型和经理。

class StateManager(models.Manager):
    def get_by_natural_key(self, name):
        return self.get(name=name)


class State(models.Model):

    class Meta:
        verbose_name = "State"
        verbose_name_plural = "States"
        permissions = (
            ('access_state', 'Can access States'),
        )

    COUNTRIES = (
        ('India', 'India'),
        ('USA', 'USA'),
        ('Thailand', 'Thailand'),
    )

    # Managers
    objects = StateManager()

    # Database fields
    name = models.CharField(
        'Name',
        max_length=100,
        unique=True,
        help_text='''
        100 chars max
        '''
    )
    code = models.CharField(
        'Code',
        max_length=10,
        unique=True,
        help_text='''
        10 chars max
        ''',
        null=True, blank=True
    )
    country = models.CharField(
        max_length=50,
        default="India",
        choices=COUNTRIES,
        blank=False,
        null=False
    )

    def __str__(self):
        return self.name

    def natural_key(self):
        return self.name

---

我的夹具文件如下

    [
    {
        "model": "parties.state",
        "fields": {
            "name": "Andaman and Nicobar",
            "code": "AN",
            "country": "India"
        }
    },
    {
        "model": "parties.state",
        "fields": {
            "name": "Andhra Pradesh",
            "code": "AP",
            "country": "India"
        }
    },
]

---

我早些时候已将数据转储到fixture文件中。 但是当我现在尝试加载夹具时，我收到以下错误...

Traceback (most recent call last):
.....
.....
  TypeError: get_by_natural_key() takes 2 positional arguments but 20 were given
.....
.....

  File "/home/parijath/Projects/virtualenv/django18/lib/python3.4/site-packages/django/core/serializers/base.py", line 195, in build_instance
    obj.pk = Model._default_manager.db_manager(db).get_by_natural_key(*natural_key).pk
django.core.serializers.base.DeserializationError: Problem installing fixture '/home/parijath/Projects/django_projects/webportal18_multipleapps/parties/fixtures/states.json': get_by_natural_key() takes 2 positional arguments but 20 were given

Answer 1

natural_key方法应该返回一个元组，而不是一个字符串。

def natural_key(self):
    return (self.name,)

如果natural_key是一个字符串"Andaman and Nicobar"而不是一个元组('Andaman and Nicobar',)那么*natural_key将解压缩字符串中的每个字符作为一个单独的参数。 与self ，它会从您的错误消息中提供20个参数。