Django. Save Model Method to different model

Question

I have a data Model and I want to save the value of amount and the value of total_amount method into payment method to have a record of payment into database.

** data/models.py **

class Data(models.Model):
    """ Model of Data"""
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    document = models.FileField(upload_to='documents/%Y/%m/%d')
    uploaded_at = models.DateTimeField(auto_now_add=True)
    amount = models.DecimalField(default=0, max_digits=6, decimal_places=2,
                                 blank=True, null=True)

    def total_amount(self):
        return Data.objects.filter(user=self.user).aggregate(Sum('amount'))['amount__sum']

payment/models.py

class Payment(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    email = models.EmailField()
    created = models.DateTimeField(auto_now=True)
    updated = models.DateTimeField(auto_now=True)
    paid = models.BooleanField(default=False)
    amount = models.DecimalField(default=0, max_digits=6, decimal_places=2,
                                 blank=True, null=True)

payments/views.py

def payment_create(request):
    user = request.user
    data = Data.objects.filter(user=user)
    if request.method == 'POST':
        form = PaymentCreateForm(request.POST)
        if form.is_valid():
            payment = form.save()

            return render(request,
                          'payments/created.html',
                          {'payment': payment})
    else:
        form = PaymentCreateForm()
        # template and context
        template = 'payments/create.html'
        context = {'form': form,
                   'data': data
                   }
    return render(request,
                  template,
                  context
                  )

I edit the question and put the views.py. I want to make the Data Model amount also save to the Payment method amount. — jmrcas
– jmrcas, Commented May 2, 2020 at 13:23

Navid Zarepak · Accepted Answer · 2020-05-02 14:27:14Z

2

Signals are a good option to achieve something like this. Using a post_save signal you can call a function whenever a new Data has been created and you can create a Payment instance there:

from django.db.models.signals import post_save
from django.dispatch import receiver

@receiver(post_save, sender=Data)
def create_payment(sender, instance, created, **kwargs):
    if created:
        # instance points to the new Data object created
        Payment.objects.create(amount=instance.total_amount()) # and any extra data you need

answered May 2, 2020 at 14:27

Navid Zarepak

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2 Comments

jmrcas Over a year ago

thanks, it's close to solve my problem. but what I want is when the user fill up the payment form the total amount from data.total_amount will automatic to save to payment amount.

Navid Zarepak Over a year ago

you mean amount field for Data model or amount field for Payment models? you can do both in the signal. doesn't matter creating a new instance for another model or just updating the same instance using instance.amount = instance.total_amount() and then instance.save()

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