python - Django:form_valid 和模型验证

Question

我正在 Django 中创建一个汽车预订应用程序。用户可以为给定的汽车创建预订。这发生在 /reservation/<car_id>/add .此表单不包含 Car 字段，因为 id 在 URL 中给出。现在我想向 Reservation 模型添加验证，这样预订就不会重叠。我有以下代码(最小版本):

# models.py

class Car(models.Model):
    name = models.CharField(max_length=200)


class Reservation(models.Model):
    car = models.ForeignKey(Car, on_delete=models.CASCADE)
    owner = models.ForeignKey(User, on_delete=models.CASCADE)
    start_time = models.DateTimeField()
    end_time = models.DateTimeField()

    def clean(self):
        # Check if overlaps with other reservations in self.car.reservation_set

# views.py

class ReservationAdd(LoginRequiredMixin, CreateView):
    template_name = 'reservation/reservation_add.html'
    model = Reservation
    form_class = ReservationAddForm

    def form_valid(self, form):
        form.instance.car = Car.objects.get(pk=self.kwargs['car_id'])
        form.instance.owner = self.request.user
        return super().form_valid(form)

# forms.py

class ReservationAddForm(forms.ModelForm):

    class Meta:
        fields = ('start_time', 'end_time')
        model = Reservation

现在我在 Reservation.clean 收到以下错误方法:

reservation.models.Reservation.car.RelatedObjectDoesNotExist: Reservation has no car.

在我看来 clean方法在 form_valid 之前被调用方法。所以我认为我的设计并不完全正确。执行此操作的正确方法是什么？

Answer 1

是的。 form_valid 表示“表单被确认为有效后运行的代码”。

您需要进行一些更改。首先，将验证移至 ReservationAddForm 本身；其次，将 Car 实例传递到该表单中。所以:

class ReservationAddForm(forms.ModelForm):

    class Meta:
        fields = ('start_time', 'end_time')
        model = Reservation

    def __init__(self, *args, **kwargs):
        self.car = kwargs.pop('car')
        super().__init__(*args, **kwargs)

    def clean(self):
        ... do something with self.car

class ReservationAdd(LoginRequiredMixin, CreateView):
    template_name = 'reservation/reservation_add.html'
    model = Reservation
    form_class = ReservationAddForm

    def get_form_kwargs(self):
        self.car = Car.objects.get(pk=self.kwargs['car_id'])
        kwargs = super().get_form_kwargs()
        kwargs['car'] = self.car
        return kwargs

    def form_valid(self, form):
        form.instance.car = self.car
        form.instance.owner = self.request.user
        return super().form_valid(form)