CODEWITHSUNDEEP
djangodjango-modelsdjango-signals
Niladry Kar
Niladry Kar

Reputation: 1203

Changing pre_save signal into post_save?Django

This are my models:

class Purchase(models.Model):
  Total_Purchase = models.DecimalField(max_digits=10,decimal_places=2,blank=True, null=True)


class Stock_Total(models.Model):
    purchases   = models.ForeignKey(Purchase,on_delete=models.CASCADE,null=True,blank=False,related_name='purchasetotal') 
    stockitem   = models.ForeignKey(Stockdata,on_delete=models.CASCADE,null=True,blank=True,related_name='purchasestock') 
    Total_p     = models.DecimalField(max_digits=10,decimal_places=2,null=True,blank=True)

I have done this in my pre_save signal:

@receiver(pre_save, sender=Purchase)
def user_created1(sender,instance,*args,**kwargs):
        total = instance.purchasetotal.aggregate(the_sum=Coalesce(Sum('Total_p'), Value(0)))['the_sum']
        instance.Total_Purchase = total

I want change the pre_save signal into post_save signal..

How do I do that?and what changes I have to make in the function?

Any idea?

Thank you

Upvotes: 0

Views: 35

Answers (1)

Sergey Pugach
Sergey Pugach

Reputation: 5669

As it's operated after instance save method called you need to call it again in order to save the changes. But you need to use the update method instead of save in order to prevent save recursion.

@receiver(post_save, sender=Purchase)
def user_created1(sender,instance, created=False, *args,**kwargs):
    total = instance.purchasetotal.aggregate(the_sum=Coalesce(Sum('Total_p'), Value(0)))['the_sum']
    Purchase.objects.filter(pk=instance.pk).update(Total_Purchase=total)

Upvotes: 1

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