django: recursion using post-save signal - django

Question

Here's the situation:
Let's say I have a model A in django. When I'm saving an object (of class A) I need to save it's fields into all other objects of this class. I mean I need every other A object to be copy of lat saved one.
When I use signals (post-save for example) I get a recursion (objects try to save each other I guess) and my python dies.
I men I expected that using .save() method on the same class in pre/post-save signal would cause a recursion but just don't know how to avoid it.
What do we do?

Answer 1

#ShawnFumo Disconnecting a signal is dangerous if the same model is saved elsewhere at the same time, don't do that !
#Aram Dulyan, your solution works but prevent you from using signals which are so powerful !
If you want to avoid recursion and keep using signals (), a simple way to go is to set an attribute on the current instance to prevent upcoming signals firing.
This can be done using a simple decorator that checks if the given instance has the 'skip_signal' attribute, and if so prevents the method from being called:
from functools import wraps
def skip_signal():
def _skip_signal(signal_func):
#wraps(signal_func)
def _decorator(sender, instance, **kwargs):
if hasattr(instance, 'skip_signal'):
return None
return signal_func(sender, instance, **kwargs)
return _decorator
return _skip_signal
We can now use it this way:
from django.db.models.signals import post_save
from django.dispatch import receiver
#receiver(post_save, sender=MyModel)
#skip_signal()
def my_model_post_save(sender, instance, **kwargs):
# you processing
pass
m = MyModel()
# Here we flag the instance with 'skip_signal'
# and my_model_post_save won't be called
# thanks to our decorator, avoiding any signal recursion
m.skip_signal = True
m.save()
Hope This helps.

Answer 2

This will work:
class YourModel(models.Model):
name = models.CharField(max_length=50)
def save_dupe(self):
super(YourModel, self).save()
def save(self, *args, **kwargs):
super(YourModel, self).save(*args, **kwargs)
for model in YourModel.objects.exclude(pk=self.pk):
model.name = self.name
# Repeat the above for all your other fields
model.save_dupe()
If you have a lot of fields, you'll probably want to iterate over them when copying them to the other model. I'll leave that to you.

Answer 3

Another way to handle this is to remove the listener while saving. So:
class Foo(models.Model):
...
def foo_post_save(instance):
post_save.disconnect(foo_post_save, sender=Foo)
do_stuff_toSaved_instance(instance)
instance.save()
post_save.connect(foo_post_save, sender=Foo)
post_save.connect(foo_post_save, sender=Foo)