Question

我在尝试将数据添加到django模型中的many2many字段时遇到意外错误。我不确定为什么我没有收到相关数据（payment_method）

对于以下型号

class PaymentMethod(models.Model):
    MONTHLY_DIRECT_DEBIT = 'MDD'
    CASH_OR_CHEQUE = 'CAC'
    QUARTERLY_DIRECT_DEBIT = 'QDD'
    PAYMENT_CHOICES = (
        (MONTHLY_DIRECT_DEBIT, 'Monthly Direct Debit'),
        (CASH_OR_CHEQUE, 'Cash or Cheque'),
        (QUARTERLY_DIRECT_DEBIT, 'Quarterly Direct Debit'),
    )
    unique_id = models.CharField(max_length=3, choices=PAYMENT_CHOICES)
    name = models.CharField(max_length=255, unique=True)

class Tariff(models.Model):
    name = models.CharField(max_length=255)
    supplier = models.ForeignKey(Supplier)
    payment_method = models.ManyToManyField(PaymentMethod)
    region = models.ManyToManyField(Region)

        class Meta:
    unique_together = ('name', 'supplier')

class Supplier(models.Model):
unique_id = models.IntegerField(unique=True)
name = models.CharField(max_length=255, unique=True)

我正在尝试通过以下方式将付款方式数据添加到关税中：

supplier = Supplier.objects.get(unique_id=region.default_supplier.unique_id)
payment_method_instance = PaymentMethod.objects.get(unique_id=payment_method['id'])
tariff, created = Tariff.objects.get_or_create(name=tariff, supplier=supplier)
    if created:
        sys.stdout.write('Tariff {} not found for Supplier: {}\n'.format(tariff, supplier))
        tariff.payment_method.add(payment_method_instance)

当我尝试通过以下方式访问关税的付款方式时，我收到以下错误：

>>> tariff1.payment_method
Out[4]: <django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager at 0x11326c710>
>>> tariff.payment_method.unique_id
Traceback (most recent call last):
  File "", line 3066, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-5-a0370f309c95>", line 1, in <module>
    tariff.payment_method.unique_id
AttributeError: 'ManyRelatedManager' object has no attribute 'unique_id'

Answer 1

payment_method模型中的Tariff字段是一个M2M字段，因此它不会返回一个对象，它将返回一组对象。因此，您无法访问.unique_id attr，因为它不是PaymentMethod对象。您可以获取与当前unique_id对象相关的所有PaymentMethod个对象的Tariff值：

>>> tariff1.payment_method.all().values_list('unique_id', flat=True)

Django Many2many字段属性错误

1 个答案: