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I am using Django's pre_save signal to implement auto_now_add. There is a lot of discussion on the internet on why you should or shouldn't implement it yourself. I do not appreciate comments on this. Neither on whether I should be rewriting the save function (I have a lot of models that use auto_now_add so using signals makes sense).
My question is:
I would like to check if the instance is created or updated. According to some sources on the internet this can be done by testing if kwargs['created'] is True. However 'created' does not appear in my kwargs even though the instance is newly created. I was just wondering if it has ever existed or that it has disappeared magically. I know I could also test if kwargs['instance'].id is set (this in fact works for me), but I'd like to know if kwargs['created'] still exists.
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There are two ways to send signals in Django. To send a signal, call either Signal. send() (all built-in signals use this) or Signal. send_robust() .
The Django Signals is a strategy to allow decoupled applications to get notified when certain events occur. Let's say you want to invalidate a cached page everytime a given model instance is updated, but there are several places in your code base that this model can be updated.
Django Signals - post_delete()To notify another part of the application after the delete event of an object happens, you can use the post_delete signal.
pre_save. This is sent at the beginning of a model's save() method. Arguments sent with this signal: sender.
Primary key attribute usually assigned by the database when the instance saved first time. So you can use something like if instance.pk is None
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