如何在 forms.py 和 views.py 中创建冷冻 class 字段时更改父 class 中的字段？

Question

I'm was creating ModelForm I try to make change the parent class while saving child class fields to the database, in the views.py I made but it didn't save to the database. here is my model.py

class Table(models.Model):
    restaurant = models.ForeignKey(Restaurant, on_delete=models.CASCADE)
    book = models.BooleanField(default=False)

class People(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, null=True)
    taple = models.OneToOneField(Table, on_delete=models.CASCADE, null=True, blank=True)

@receiver(post_save, sender=User)
def update_people_profile(sender, instance, created, **kwargs):
    try:
        instance.people.save()
    except ObjectDoesNotExist:
        People.objects.create(user=instance)

Class People is the child class and Table is the parent class so I'm using People class for making forms. here is my forms.py

class Booking(forms.ModelForm):

    class Meta:
        model = People
        fields = [
            'taple',
        ]

So I want to make True book field in Table class and save it to the database when saving Booking form. here is my views.py

def booking(request):
    if request.method == 'POST':
        try:
            people_instance = People.objects.get(user=request.user)
        except Table.DoesNotExist:
            people_instance = People(user=request.user)
        form = Booking(request.POST, instance=people_instance)
        if form.is_valid():
            user = form.save(commit=False)
            user.taple.booking = True
            user.refresh_from_db()
            user.user = request.user
            user.taple = form.cleaned_data.get('taple')
            user.save()
            print(user.taple.booking, user.taple.id)
            return redirect('booked')
    else:
        form = Booking()
    return render(request, 'main/booking.html', {'form': form})

Any Idea?

Answer 1

What I understand from the snippets is that you want to be able to record if a table is booked (book Boolean Field in your Table model and if so by whom, which is the object of your People model.

If my understanding is correct, then I don't think you really need a join table (People model). Instead, I would change your model as follow:

class Table(models.Model):
    restaurant = models.ForeignKey(Restaurant, on_delete=models.CASCADE)
    booked_by = models.OneToOneField(User, null=True, on_delete=models.SET_NULL, related_name='table_booked')

    @property
    def is_booked(self):
        # This returns True if booked_by is set, False otherwise
        return self.booked_by_id is not None

This way you don't need the People model. The property decorator will allow you to use is_booked as a calculated field. Also, note the related name which will be used in the form:

class BookingForm(forms.ModelForm):
    table_booked = forms.ModelChoiceField(queryset=Table.objects.filter(booked_by__isnull=True))
    class Meta:
        model = User
        fields = ['table_booked',]

In the form, you will see that we define a custom queryset for table_booked. THe aim is to filter for free tables only.

Then you can hopefully simplify as well your view as follow:

Update: As table_booked is a reverse foreign key, we actually need to save the table object which contains the relation. Here is the modified view:

@login_required
def booking(request):
    form = BookingForm(request.POST or None, instance=request.user)
    if form.is_valid():
        user = form.save(commit=False)
        tbl = form.cleaned_data['table_booked']
        tbl.booked_by = request.user
        tbl.save()
        user.save()
        print(request.user.table_booked.id, request.user.table_booked.is_booked)
        return redirect('/')
    return render(request, 'booking/booking.html', {'form': form})

Note: I haven't tested the code so there could be some typos but that should help you getting started.