Django CreateView-created_by，modified_by mixin不起作用

Question

我遵循了有关CBV的spapas教程，并尝试将mixin应用于创建视图。但是看起来它无法正确评估用户外键的if。form.invoice.requester，因为它始终显示：RelatedObjectDoesNotExist，它指向在 if 行中评估的字段。

有什么问题吗？

views.py

class AuditableMixin(object, ):
def form_valid(self, form, ):
    if not form.instance.requester:
        form.instance.requester = self.request.user
    form.instance.modified_by = self.request.user
    return super().form_valid(form)

class NewOrderView(LoginRequiredMixin, PermissionRequiredMixin, AuditableMixin, generic.CreateView):
    permission_required = 'orders.add_order'
    form_class = NewOrderForm
    model = Order
    title = 'New Order'
    extra_context = {'title': title}

forms.py

class NewOrderForm(forms.ModelForm):
    class Meta:
        model = Order
        widgets = {
            'order_details': forms.Textarea,
        }
        exclude = (
            'status',
            'invoice',
            'requester',
            'modified_by',
        )

models.py

class Order(models.Model):
STATUS_CHOICES = (
    ('open', 'Open'),
    ('inprogress', 'In Progress'),
    ('rejected', 'Rejected'),
    ('closed','Closed'),
    ('resolved','Resolved'),
)

subject = models.CharField(
    max_length=30,
)

requester = models.ForeignKey(
    User,
    on_delete=models.PROTECT,
    related_name='orders',

)

order_details = models.TextField(

)

created = models.DateTimeField(
    auto_now_add=True,
)

updated = models.DateTimeField(
    auto_now=True,
)

status = models.CharField(
    max_length=12,
    default='open',
    choices= STATUS_CHOICES,
)

invoice = models.ForeignKey(
    Invoice,
    on_delete=models.PROTECT,
    blank= True,
    null=True,
    related_name='orders',
)

modified_by = models.ForeignKey(
    User,
    on_delete=models.PROTECT,
    related_name='orders_modified',
)

def __str__(self):
    return self.subject

def get_absolute_url(self):
    return reverse('Order_Detail', args=[str(self.pk)])

class Meta:
    ordering = ['-created']

谢谢。

Answer 1

在模型上调用ForeignKey对象时，实际上是在告诉Django执行查询以获取相关对象。要检查该关系是否存在，您应该检查<fieldname>_id，它是字段的实际名称：

if not form.instance.requester_id:
    form.instance.requester = self.request.user

这样，如果requester_id是None，则您将不会执行查询，而会出现RelatedObjectDoesNotExist错误。