Re: How to implement pre-save operations for inlines in the admin interface?

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Hi,

On Thu, 15 Nov 2012 18:15:37 +0100 Carsten Fuchs
<carsten.fuchs@cafu.de> wrote:
> Am 15.11.2012 17:52, schrieb Arnold Krille:
> > On Thursday 15 November 2012 17:12:09 Carsten Fuchs wrote:
> >> [...]
> >> (Note that it is not enough to consider the Period that changed --
> >> rather, it is the 'end' in *another* period (the one "before" it)
> >> that must be modified and saved, too.)
> >> What is the proper hook or where the best place to do this?
> > Why do you want to do this only in the admin interface?
> > Its a generic thing: every time you save/change a period you should
> > set the end-date of the previous one. So I would do this with a
> > post-save hook (aka signal) directly in the models.py. Or maybe
> > even subclass your models save- operation.
> Well, I realize that this would be useful also generically, outside
> of the admin interface.

Even if you do not need it outside the admin-interface (in this
project), from the logic this belongs to the model, not into some view.

> Alas, if e.g. I overrode the save() method of the Period class, is it
> safe to access *another* Period instance from there?

Yep, thats save.

If you use a db that has transactions, both the change to the other
object should be rolled back when saving of the current objects fails
as it should all end up in one transaction. :-)

> I don't really fully understand how the admin interface works when a
> model with inlines is saved, but I suspect that the inlines are saved
> in a loop. But if in an early iteration of the loop I modified
> another instance that is routinely saved *again* in a later iteration
> of the loop, it will be a bug.

I can't really comment on the admin interfaces working as we use that
only for the stuff only a superuser has rights. Everything else is
edited in our frontend-code.
But saving inlines in the admin interface should be the same as saving
forms with formsets underneath.

Have fun,

Arnold