Allow class based views to be included in urls.py by name as a string

[Tim Anderegg]

Class based views currently have to be imported into urls.py and then added to urlpatterns using ClassBasedView.as_view().

It would be relatively trivial, it seems, to add functionality to the method 'get_callable' in django.core.urlresolvers that uses inspect.isclass to determine if the lookup_view refers to a class, and if so set lookup_view = lookup_view.as_view(), throwing an exception if lookup_view is a class but the method as_view() doesn't exist.

This would help cleanup urls.py when using class based views, and be more consistent with how function based views are handled. Is there any reason not to do this? If people support this I will submit a patch.

[Aymeric Augustin]

Importing views by name in URLconfs has a big drawback: import errors are delayed until runtime. Resulting tracebacks can be confusing. I'd prefer to move away from identifying views by name. Hence I'm -0 on this proposal.

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I also have a backwards compatibility nitpick. Technically, a view can be any callable, including a class. The following class is a valid Django view:

from django.http import HttpResponse

class HelloWorld(HttpResponse):
    def __init__(self, request):
        return super(HelloWorld, self).__init__('hello world', content_type='text/plain')

I don't know if this pattern is common or even useful, but it's something that currently works, and your proposal would break it.

EDIT: after a quick poll on IRC, at least one person confesses having used this pattern, and knows other people who have too.

[Alex Gaynor]

I'm wontfixing this. It was an intentional design decision for CBVs not to have any special support in the URL system or elsewhere. Making this change would complicate the view contract, which ATM is very simple.

For bonus points I'll add that I consider the string import path thing in urls to be an anti-pattern and who's use should be discouraged.

[Tim Anderegg]

Fair enough, maybe I should just abandon string import paths in general then. Thanks all,

Tim

[Aymeric Augustin]

One last note: you can use the following pattern:

class MyClassBasedView(View):
    # ...

my_class_based_view = MyClassBasedView.as_view()

and then refer to my_class_based_view by name in the URLconf. Granted, it's one line of boilerplate.