I understand that we can use reverse() in FBV and reverse_lazy() in CBV. I understand that we have to use reverse_lazy() in CBV as the urls are not loaded when the file is imported (Ref: Reverse_lazy and URL Loading?)
What I don't understand is:
How are the urls loaded when we call reverse from the FBV? As when we import the views at the top of the urls.py in a Django app, urlpatterns list is yet to be evaluated. How does reverse() for FBV work but not for CBV?
Consider these two ways of defining the success_url. The first is commented out, the second is the function:
class NewJobCBV(LoginRequiredMixin, CreateView):
template_name = 'company/job.html'
form_class = newJobForm
# success_url = reverse_lazy('newJob')
def get_success_url(self, **kwargs):
return reverse("newJob")
@CoffeeBasedLifeform : you are right, class attributes are evaluated on import, I checked after reading your answer. So,
success_url we have to use reverse_lazy(). reverse().Now it is crystal clear.
Thanks CoffeeBasedLifeform :)
#importme.py
def a():
print("FUNCTION HELLO")
class B():
print("CLASS HELLO")
>>> import importme
>>> CLASS HELLO
Edit: The reason: The class creation process involves executing the body of the class.
The class body is executed (approximately) as
exec(body, globals(), namespace). [...] Once the class namespace has been populated by executing the class body, the class object is created by callingmetaclass(name, bases, namespace, **kwds).
https://docs.python.org/3/reference/datamodel.html?highlight=metaclass#executing-the-class-body
My original answer text. You can ignore it - I'm just leaving it in because mirek's comment was a direct response to it:
Class attributes are evaluated on import. The answer to when or exactly how that happens, resides within the depths of python's import system.
Just understand the difference:
reverse() returns a string & reverse_lazy() returns an <object>