Ok, yes, this all makes sense now. Thanks for the explanation!
Margie On Mar 24, 3:32 am, Russell Keith-Magee <freakboy3...@gmail.com> wrote: > On Tue, Mar 24, 2009 at 6:10 PM, Thomas Guettler <h...@tbz-pariv.de> wrote: > > > Hi, > > > book2.publisher is an attribute which was created before you deleted it. > > If you get book2 again from Book.objects, this attribute would not exist > > anymore. > > > I have not looked at the underlaying django source, but I guess that > > remove(obj) removes the attribute from obj. > > > But clear() can't do this, since it does not have a reference to all > > affected objects. > > Your guess at the implementation is correct. In the implementation of > remove(), we have a handle to the object that is being removed, so we > are able to update the value of the publisher attribute on the object. > In the case of clear(), we don't have a handle to the object being > updated, so we can't update the publisher attribute. > > Two other interesting manifestations/side effects of this behaviour > that are worth note: > > * If you have a second reference to book2, it won't be updated in the > case of remove(): > > >>> book1 = pub.book_set.create(title="title1") > >>> otherbook1 = Book.objects.get(title="title1") > ... > >>> otherbook1.publisher > <Publisher: pub1> > >>> pub.book_set.remove(book1) > >>> book1.publisher > >>> otherbook1.publisher > > <Publisher: pub1> > > * If you re-retrieve book2, the publisher attribute will be correct:>>> > pub.book_set.clear() > >>> book2.publisher > <Publisher: pub1> > >>> otherbook2 = Book.objects.get(title="title2") > >>> otherbook2.publisher > > # value is none, as expected > > Yours, > Russ Magee %-) --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
