Identify the changed fields in django post_save signal

Question

I\'m using django\'s post_save signal to execute some statements after saving the model.

class Mode(models.Model):
    name = models.CharField(max_length=5)
         


        

Answer 1

in post_save method you have kwargs argument that is a dictionary and hold some information. You have update_fields in kwargs that tell you what fields changed. This fields stored as forzenset object. You can check what fields changed like this:

@receiver(post_save, sender=Mode)
def post_save(sender, instance, created, **kwargs):
    if not created:
        for item in iter(kwargs.get('update_fields')):
            if item == 'field_name' and instance.field_name == "some_value":
               # do something here

But there is an issue in this solution. If your field value for example was 10, and you update this field with 10 again, this field will be in update_fields again.