Given both the docs for get_absolute_url and reverse demonstrate using string references only, I think adding in clarification of why it's preferred is worthwhile.
I still find it surprising how often I need to tell people on #django to not import models just to reference them in relation fields... -- Curtis On 1 September 2013 17:00, Jorge Cardoso Leitao <jorgecarlei...@gmail.com>wrote: > The way I stumbled across this problem was: > > 1. views imports models and forms (both are normally needed) > > 2. forms imports models (for ModelForm) > > 3. models imports views (for get_absolute_url), e.g.: > > *import views* > *class MyModel(models.Model):* > * get_absolute_url(reverse(views.myview))* > > which leads to a circular dependency of the form > views->forms->models->views. > > I searched and there are some questions raised in stackoverflow about it, > e.g. > this<http://stackoverflow.com/questions/5238658/django-cannot-import-name> > , this<http://stackoverflow.com/questions/7684408/django-cannot-import-name-x> > . > This is avoided by removing one of the imports, and in this > case the candidate is 3., replacing it with a string (e.g. 'views.myview'). > > I propose that we add a note on the documentation of > get_absolute_url<https://docs.djangoproject.com/en/dev/ref/models/instances/#get-absolute-url> > explaining that get_aboslute_url should be coded by returning reverses of > strings and > not of functions or classes to avoid circular dependencies. > > There is a ongoing > thread<https://groups.google.com/forum/#!searchin/django-developers/models$20urls/django-developers/fmnDnCPsEHk/GItiWQ6iyRQJ> > about > get_absolute_url and I think these problems are > somewhat related: this circular dependency is a valid mistake from a > Django user because models are depending on views, views on forms, forms > on models. > > Another reason why I think this should be documented is that circular > dependencies > are difficult to debug, specially when they occur after modules are > imported like *import module.* > > This also makes the documentation more consistent: Foreign > Key<https://docs.djangoproject.com/en/1.5/ref/models/fields/#foreignkey> > already > warns about circular dependencies: > > "This sort of reference can be useful when resolving circular import > dependencies between two applications." > > In summary, I agree that the url's "anti-circular dependency" is correctly > fixed from the implementation point of view by allowing strings, > what I'm proposing is just to document why users should use it, i.e. what > they are useful for, specially in the models' get_absolute_url. > > If no one objects, I can do this. > > Regards, > Jorge > > -- > You received this message because you are subscribed to the Google Groups > "Django developers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to django-developers+unsubscr...@googlegroups.com. > To post to this group, send email to django-developers@googlegroups.com. > Visit this group at http://groups.google.com/group/django-developers. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "Django developers" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To post to this group, send email to django-developers@googlegroups.com. Visit this group at http://groups.google.com/group/django-developers. For more options, visit https://groups.google.com/groups/opt_out.
