Re: ModelAdmin with inlines: How to learn if/what has changed before the models are saved?

Hi Alex,

Am 20.12.2014 um 22:47 schrieb Alex Haylock:
> Take a look at the Django signal dispatcher:
> https://docs.djangoproject.com/en/dev/topics/signals/
>
> Specifically, the 'update_fields' argument passed to the 'pre_save'
> signal should provide what you need:
>
> https://docs.djangoproject.com/en/dev/ref/signals/#django.db.models.signals.pre_save

Many thanks for your reply!

While I seem to understand signals generally, I followed Collin's
suggestion, because the ModelAdmin class already has so many readily
available customization callbacks, so that this eventually looked a bit
more straightforward to me.

Also, the big question that occurred to me when I (re-)read the signals
documentation that you linked above was this description for the
`update_fields` argument:
"The set of fields to update explicitly specified in the save()
method. None if this argument was not used in the save() call."

To be honest, I did not fully set it up to try it out, but in the
ModelAdmin source I saw that the model's save() method is plainly
called, without any explicit parameters. This would have rendered the
`update_fields` useless, and left me with no way to figure out what has
changed in the model when the pre_save signal is received, right?

Best regards,
Carsten

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