更改表单上模型的默认值

Question

如何在forms.py类中，覆盖模型category的默认值，而不将其添加到html表单中？

forms.py

class FastForm(forms.ModelForm):
    class Meta:
        model = Orders
        fields = ['device']

models.py

class Orders(models.Model):
    device = models.CharField(max_length=150)
    category = models.ForeignKey('Category', default=1, on_delete=models.PROTECT)

class Category(models.Model):
    category = models.CharField(max_length=150, db_index=True)

UPD

观看次数

class OrderAddView(TemplateView):
    template_name = 'orders/order_add.html'

    def get(self, request, *args, **kwargs):
        context = super().get_context_data(**kwargs)       
        formOne = FastForm
        context.update({'formOne': formOne})
        return self.render_to_response(context)

    def post(self, request, *args, **kwargs):
        formOne = FastForm(self.request.POST)        

        if formOne.is_valid():
            form_update = formOne.save(commit=False)
            form_update.save()            
            return HttpResponseRedirect('orders_home')
        else:
            print('NotValid')