基于另一个模型的实例自动创建模型的实例

Question

I want to create 4 instances of tyres and 1 instance of engine when I create instance of car model here is my model code

class Car(models.Model):
    company=models.CharField(max_length=25)
    car_model = models.CharField(max_length = 25)
    year = models.IntegerField()

class Engine(models.Model):
    car=models.OneToOneField(Car)
    engine_type=models.CharField(max_length = 15)
    no_cylinders=models.IntegerField()
    state=models.CharField(max_length = 15)
class Tyre(models.Model):  
    car=models.ForeignKey(Car)
    tyre_material=models.CharField(max_length = 15)
    position=models.CharField(max_length = 10)  #ex front right back left 
    state=models.CharField(max_length = 15)

and the form for car

class car_form(forms.ModelForm):
    
    class Meta:
        model = Car
        fields = (
            'comapany',
            'car_model',
            'year'
            )

    def save(self, commit=True):
        obj=car_form.save()
        obj.company = self.cleaned_data['comapany']
        obj.car_model = self.cleaned_data['car_model']
        obj.year = self.cleaned_data['year']
        
        if commit:
            obj.save()

    return obj

and here is my view

def car_create(request):
    if request.method =='POST':
        form = car_form(request.POST)
        if form.is_valid():
            form.save()
            return redirect("/")
        else :
            return render(request, 'agency/car_form.html', 
                          {'form': form})
    else:
        form = car_form()

        args = {'form': form}
        return render(request, 'agency/car_form.html', args)

What should I change in my code?

Answer 1

You could create your instances based on your parent instance like :

Views.py

...
    new_car = form.save()
    engine = Engine.objects.create(car=new_car)
    for i in range(4):
        tyre = Tyre.objects.create(car=new_car)
...

Answer 2

最好的办法是使用信号