问题
I'm writing a view that inherits from ListView, and am trying to restrict the view to logged-in users.
https://docs.djangoproject.com/en/dev/topics/class-based-views/#decorating-in-urlconf says that decorating with login_required in the URLconf "applies the decorator on a per-instance basis. If you want every instance of a view to be decorated, you need to take a different approach" -that approach being to decorate the dispatch method in the view code.
I thought I knew the difference between a class and an instance but this phrase doesn't mean anything to me. Could someone clarify? Apart from having a decorator in the URLconf as opposed to in your class definition, what are the differences between the two approaches?
The paragraph above that link seems to answer the question: "Since class-based views aren't functions, decorating them works differently depending on if you're using as_view or creating a subclass."
Really?? I seem to be able to use the URLconf approach with my subclass of ListView.
回答1:
Imagine you have the following class based view:
class PostListView(ListView):
model = Post
ProtectedPostListView = login_required(PostListView.as_view())
and your urls.py:
url(r'posts$', ProtectedPostListView)
If you use this approach then you lose the ability to subclass ProtectedPostListView e.g
class MyNewView(ProtectedPostListView):
#IMPOSSIBLE
and this is because the .as_view() returns a function and after applying the login_required decorator you are left with a function, so subclassing is not possible.
On the other hand if you go with the second approach i.e use the method decorator the subclassing is possible. e.g
class PostListView(ListView):
model = Post
@method_decorator(login_required)
def dispatch(self, *args, **kwargs):
return super(PostListView, self).dispatch(*args, **kwargs)
class MyNewView(PostListView):
#LEGAL
来源：https://stackoverflow.com/questions/12132819/whats-the-difference-between-the-two-methods-of-decorating-class-based-views