How to add default value in queryset? - django

Question

I have a moneybook, moneylog models
and moneylog get relation with moneybook manytomany.
moneybook = models.ForeignKey(
moneybook_models.Moneybook, on_delete=models.CASCADE)
pay_day = models.DateTimeField(default=NOW)
payer = models.ForeignKey(
user_models.User, on_delete=models.CASCADE, related_name="payer")
dutch_payer = models.ManyToManyField(
user_models.User, related_name="dutch_payer", blank=True)
price = models.IntegerField()
category = models.CharField(max_length=10)
memo = models.TextField()
I want payer default save in dutch_payer if user choose or not.
and this is my forms.py
class CreateMoneylogForm(forms.ModelForm):
class Meta:
model = models.Moneylog
fields = (
"pay_day",
"payer",
"dutch_payer",
"price",
"category",
"memo",
)
widgets = {
"dutch_payer": forms.CheckboxSelectMultiple
}
def save(self, *args, **kwargs):
moneylog = super().save(commit=False)
return moneylog
views.py
class moneylog_create(FormView):
form_class = forms.CreateMoneylogForm
template_name = "moneylogs/create.html"
def form_valid(self, form):
moneylog = form.save()
moneybook = moneybook_models.Moneybook.objects.get(
pk=self.kwargs["pk"])
form.instance.moneybook = moneybook
if moneylog.payer not in moneylog.dutch_payer.all():
moneylog.dutch_payer.add(moneylog.payer)
moneylog.save()
form.save_m2m()
return redirect(reverse("cores:home"))
as you see.
if moneylog.payer not in moneylog.dutch_payer.all():
moneylog.dutch_payer.add(moneylog.payer)
moneylog.save()
form.save_m2m()
return redirect(reverse("cores:home"))
this not work.(there is no payer in dutch_payer) how can i achieve it?