Re: Acessing data on Model/Detail classes
On 6-7-2012 17:14, Fabiano Martins wrote: > 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.) Yes, and normally the clean() method is the right method, but ... > At this moment, the database relationship yet not exists, but the > "memory data relashionship" already exists. you don't have access to the request object in the clean() method. > > 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. Yes, in the form, the view and the template. But there's no relationship there either. There's simply a collection of named data and because you know the names you can make the relationship. > 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? The relationship does not exist. Observe: database <=> model <=> form <=> view <=> template |--relationship--| |-- dictionary of names --| So, in python there's no relationship between models. There are model managers that fetch the relationship from the database and return a list of objects and make it seem like there is a relationship, but the actual link is in the database. Since the products first need to know the primary key of the Master to make the relationship, the Master needs to be saved first. I would investigate the post_save signal. -- Melvyn Sopacua -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
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. -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: Acessing data on Model/Detail classes
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. -- Melvyn Sopacua -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
