This doesn't seem to have been resolved at all, so a couple of questions that might help things out...
On Tue, 2009-04-14 at 19:06 -0700, Emma F wrote: > I feel like there must be something very elementary that I'm missing > here, but I've been all through the documentation and can't figure it > out. > > Say an app includes three models: > > - "Products" > (includes fields: Product Name, Supplier, Cost Price, Retail Price > > - "Customers" > (includes fields: Customer Name, Address, Contact Number, Payment > Details) > > - "Orders", a list of individual orders placed with the business. > (includes fields: Product Name, Customer Name, Delivery Address, > Price, Payment Details) Is there some particular reason you want to model things this way -- denormalising the data so that the Orders model duplicates information that is already available? Sometimes denormalisation is a solution to a particular performance problem and if you have millions and millions of orders, it might be reasonable. But I suspect that isn't the case here. So why not have a ForeignKey from Orders to both Products and Customers that indicates which is the authoritative data for that information. That would seem to solve your problem immediately, since I'm assuming you already have some way of knowing which are the right Product and Customer instances and can then retrieve those. General rule runs along the line of: "normalise until it hurts, then denormalise until it works" and the second step isn't needed nearly as often as people try to make out in their initial designs. > > The Product Name and Customer Name fields in "Orders" are ForeignKey > fields linked to the relevant models. Each Order only involves one > Product and one Customer. > > My question: Is it then possible to autopopulate the other fields in > the Orders model (eg. delivery address, payment details, retail price) > with the corresponding default information associated with that > Product or Customer? I'm using hooks to the save(self) process in the > admin, and it's working fine for hard-coded values, but I can't get it > to go to the related objects for data. What is going wrong? Is an error being raise? Or are you perhaps trying to query based on the (currently non-existent) value of the Order's pk value -- which would definitely return nothing? At the point that you are trying to save an Order object, how do you know which are the appropriate Customer and Product records to be using? Regards, Malcolm --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
