Django: Can I perform two pre-save signal for same operation?

Question

Can I peform two pre-save signal in django for same operation just the sender will be diffrent in both cases...

This is my models:

   class Ledger1(models.Model):
        creation_Date = models.DateField()
        name = models.CharField(max_length=32)
        group1_Name = models.ForeignKey(Group1,on_delete=models.CASCADE,blank=True,null=True)
        Opening_Balance = models.DecimalField(max_digits=19,decimal_places=2,blank=True)
        Closing_balance = models.DecimalField(max_digits=10,decimal_places=2,blank=True,null=True)

   class Journal(models.Model):
        Date = models.DateField()
        By = models.ForeignKey(Ledger1,on_delete=models.CASCADE,related_name='Debitledgers')
        To = models.ForeignKey(Ledger1,on_delete=models.CASCADE,related_name='Creditledgers')
        Debit = models.DecimalField(max_digits=10,decimal_places=2)
        Credit = models.DecimalField(max_digits=10,decimal_places=2)

And this I have done previously:

@receiver(pre_save, sender=Ledger1)
def update_user_closing_balance(sender,instance,*args,**kwargs):
    debit = instance.Debitledgers.aggregate(debit=Sum('Debit'))['debit']
    credit = instance.Creditledgers.aggregate(credit=Sum('Credit'))['credit']
    instance.Closing_balance = instance.Opening_Balance + debit - credit

I want to do a similar pre-save signal but the sender will be journal...And Can I have two signal for same functionality in django?

I mean to say when the ledger is updated the closing balance will be updated automatically that I have done already...

But I also want to do something like when journal is updated then also the closing balance will be updated...

Do anyone know this?

Can I call the 'update_user_closing_balance' function in that pre_save signal where sender=journal? — Niladry Kar, Oct 12 '18 at 08:24
Possible duplicate of [Consolidating multiple post\_save signals with one receiver](https://stackoverflow.com/questions/17507784/consolidating-multiple-post-save-signals-with-one-receiver) — joppich, Oct 12 '18 at 08:25
calling the function will not work, just trigger the pre_save — Vaibhav Vishal, Oct 12 '18 at 08:31

Vaibhav Vishal · Accepted Answer · 2018-10-12T08:41:44.000

1

This will trigger pre_save for related Ledger1 models

from django.db.models.signals import post_save
@receiver(post_save, sender=Journal)
def trigger_pre_save(sender, instance, *args, **kwargs):
        instance.By.save()  # trigger pre_save for By Ledger
        # or
        # post_save.send(Ledger1, instance=instance.By, created=False)
        instance.To.save() # trigger pre_save for To Ledger
        # or
        # post_save.send(Ledger1, instance=instance.To, created=False)

edited Oct 12 '18 at 08:41

answered Oct 12 '18 at 08:25

Vaibhav Vishal

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no. Before saving Journal it will save Ledger too. If its not working as expected try post_save for Journal – Vaibhav Vishal Oct 12 '18 at 08:39
Yeah post_save signal works perfectly fine...Thank you@Vaibhav Vishal – Niladry Kar Oct 12 '18 at 08:43
1

well I learned something too. I was expecting pre_save to work but guess it doesn't for created instance – Vaibhav Vishal Oct 12 '18 at 08:45

Django: Can I perform two pre-save signal for same operation?

1 Answers1