Django Admin Modelform，保存计算的相关性

Question

我在Overwritter Modelform的save（）方法中面临Django管理员的问题。

models.py

class Reservation(models.Model):
    status = models.PositiveSmallIntegerField(choices=STATUS, default=0)
    creation_date = models.DateTimeField(auto_now_add=True)
    date_start = models.DateField()
    date_end = models.DateField()
    service = models.ForeignKey(Service, on_delete=models.CASCADE)
class ReservationItem(models.Model):
    quantity = models.IntegerField()
    unit_price = models.DecimalField(max_digits=10, decimal_places=2)
    unit_tax = models.DecimalField(max_digits=10, decimal_places=2)
    row_total = models.DecimalField(max_digits=10, decimal_places=2)
    row_total_incl_tax = models.DecimalField(max_digits=10, decimal_places=2)
    reservation = models.ForeignKey(Reservation, on_delete=models.CASCADE, related_name='items')
    resource = models.ForeignKey(Resource, on_delete=models.CASCADE)

预订项目是从服务派生的，通过可用性查询，因此为管理员编写了自定义Modelform。

admin.py

class ReservationModelForm(forms.ModelForm):
    def clean(self):
        if 'service' in self.cleaned_data:
            self._check_availability()
        return self.cleaned_data
    def _check_availability(self):
        '''do some stuff an get items ad an array of ReservationItems instances created like this:
        ReservationItem(
            resource=avail_resource,
            quantity=resource_type.quantity,
            unit_price=resource.unit_price,
            unit_tax=resource.unit_price*resource.tax.percentage,
            row_total=resource.unit_price*resource_type.quantity,
            row_total_incl_tax=...
        )'''
        self.cleaned_data['items'] = items
    # then the save method
    def save(self, commit=True):
        reservation = super(ReservationModelForm, self).save(commit=commit)
        if not self.instance.id:
            service = self.cleaned_data.get('service')
            ....
            reservation.items.set(self.cleaned_data['items'], bulk=False)
         return reservation
class ReservationAdmin(admin.ModelAdmin):
   form = ReservationModelForm

现在我得到的只是一个错误： save() prohibited to prevent data loss due to unsaved related object 'reservation'。

但是我不能先保存预订，因为我需要原子保存，我该如何解决？

Answer 1

我想到了一个解决方案。我已经在预订模型temp_items中添加了一个属性，并将它们保存在交易中的模型Save（）方法中，以便我可以在Modelform save（）中提取和验证项目，并实际上保存在模型save（）方法中。它似乎很棒