Single Table Inheritance
I'm sure this subject has been beaten to death, but I haven't found an answer to a simple scenario and I'm wondering why this hasn't been addressed before. I have three models, structured like so: Document -Presentation -Spreadsheet Document is never instantiated on its own; a prime candidate for an abstract base class. However, there are times where I want to list/ search across all documents, and I'd like to be able to write Document.objects.all(). I'd then like to be able to iterate over this enumerable and have each object cast to its proper class. This is something accomplished with single table inheritance in Rails; why don't we have the equivalent in Django? I know I could just use the Document class and have a type field, but then I have to do all of the type checking legwork manually. I was hoping Django would handle normalizing/denormalizing as part of the ORM. In essence, creating its own type field automatically in the back- end and casting each object to the appropriate class based on the string value in this field. Does anyone know why this isn't available? Is there an equally efficient method of modeling this approach of which I am unaware? -- You received this message because you are subscribed to the Google Groups "Django developers" group. To post to this group, send email to django-developers@googlegroups.com. To unsubscribe from this group, send email to django-developers+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-developers?hl=en.
Re: Single Table Inheritance
Cool. Well, maybe I can look into how abstract base classes are currently implemented and see if there's a way to generate query sets for all derived classes from the parent. Thanks for the insight! On Mar 29, 12:40 pm, Carl Meyer wrote: > On 03/29/2011 12:40 PM, Jeremy Dunck wrote: > > > What about keeping abstract inheritance in this case, but allowing > > Document.objects.* to work by returning instances of the subclasses. > > Filtering, etc. would only work based on the Document base class. > > > It would mean doing some unions, but would still fit the use case > > pretty well, I think. > > I'd certainly be intrigued to look at a patch that implemented that. > > Carl -- You received this message because you are subscribed to the Google Groups "Django developers" group. To post to this group, send email to django-developers@googlegroups.com. To unsubscribe from this group, send email to django-developers+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-developers?hl=en.
