On Tue, May 23, 2017 at 3:44 PM, <[email protected]> wrote: > I have a model class, 'A_base', and a 2nd model class, 'A_derived'. When I > save an object of A_derived, I want the data from both my base and derived > class to be saved. > > Example code looks like this: > > class A_base(models.model): > name = models.CharField(max_length=50) > > class A_derived(A_base): > role = models.CharField(max_length=50) > > > So when I call save(), I want to save an instance of the derived object, > including the data in the base class into my sqlite3 database. I would like > my code to look like this: > > ... > derived_obj = A_derived.objects.get(name="john") > derived_obj.role = "parent" > derived_obj.save() > ... > > My question is whether the save method will save 'role' to the A_derived > table and save 'name' to the A_base table? Or do I have to override the > save method so that it saves 'role' and then calls the base class save > method to save 'name'? > > No, you have created two separate (but related) models. A_base has a model field of 'name', and A_derived has model fields 'name' and 'role'. Since you are inheriting from a non-abstract parent model, there is an implied OneToOne relationship between the two models, see the following: https://docs.djangoproject.com/en/1.11/topics/db/models/#multi-table-inheritance
I'm not a big fan of this implied behavior, but it hasn't been problematic for me because I make heavy use of abstract model classes. If you do not want the implied relationship between the two models, create an abstract base class matching A_base and have both of your models inherit from it (A_base would be an empty model in this case, most likely). >From a Django perspective, these two are completely independent models/entities (aside from the OneToOne relationship). A_derivied will have its own name and role. A_base also has it's own name, but will not be able to contain a role. To achieve the behavior you want, when A_derived is saved, you'll need to either create a new A_base object and set the 'name' field to the same value, or query for an existing A_base object and change/save the 'name' field. Keep in mind that the two values are not connected to each other. Changing the 'name' field on the same A_derived class later will NOT change the 'name' field on an A_base object automatically, you would need to provide such logic on one or both models, depending on the direction of the dependency you wish to create. > I tried doing this using the default save method and it created a stack > trace, so I'm guessing that I am expecting too much from the default save > method. > > Post the entire stack trace and we may be able to better illuminate the issue. -James -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CA%2Be%2BciXDpbGmmpqbcDC_iipvRVowJhuw3VcdeJsVLMAVJ5g-WQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
