Re: Acessing data on Model/Detail classes

My idea was centralize the validation in the Model to allow use it on
several clients besides the primary Web page (such as a batch program, a
web service, etc.)

At this moment, the database relationship yet not exists, but the
"memory data relashionship" already exists.

Conceptually I think that, how I can access the data that will be saved
on the Master class, I should be able to access the data that will be
save on related classes on the same transaction.

Now I've made a new test: I created a method "clean()" on Product class,
and see that from it I can't access data from Master class, and I can't
access from other instances of Product class...

Conceptually, in the Model the data of several instances of classes on
the same transaction can be treated as a set, or a object always be
individually validated on Model?

--
Fabiano Martins

Em 05-07-2012 22:03, Melvyn Sopacua escreveu:
> On 5-7-2012 21:46, Fabiano Martins wrote:
>
>> I'm novice on Django, and I have a problem that I can't resolve through
>> documentation.
>>
>> I like to make a validation on Model.clear() of the master class method based on
>> data of your detail classes, but it returns always a empty set.
>>
>> This example illustrates my problem:
>>
>> def clean(self):
>> super(Master, self).clean()
>> total = 0
>> for product in self.product_set.all():
>> total += product.value
> At clean() time nothing has been saved, so the relationship isn't there
> yet and you can't ask for it. There are a few ways to solve it in
> decreasing order:
> - Use a custom template and write some javascript that calculates the
> master value on submit.
> - Write a custom view and calculate the totals there.
> - Wrap everything in a transaction, do the validation in the post_save
> signal and roll back the transaction if the total is too low (not even
> sure this /can/ be done).
>
> Maybe others have more ideas.

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