Django views as_view() - django

Question

Example views.py:
from django.http import HttpResponse
from django.views import View
class MyView(View):
def get(self, request, *args, **kwargs):
return HttpResponse('Hello, World!')
Example urls.py:
from django.urls import path
from myapp.views import MyView
urlpatterns = [
path('mine/', MyView.as_view(), name='my-view'),
]
classmethod as_view(**initkwargs)¶
What happens when a request from the user is received?
Is the view returned from ClassView.as_view() called?
Or is an instance of Class View created?

Answer 1

The urls.py will call the callable that is passed to the path(..). Here .as_view() will thus return a function that is called. You can find the source code for this in the GitHub repositiory:
#classonlymethod
def as_view(cls, **initkwargs):
"""Main entry point for a request-response process."""
for key in initkwargs:
if key in cls.http_method_names:
raise TypeError("You tried to pass in the %s method name as a "
"keyword argument to %s(). Don't do that."
% (key, cls.__name__))
if not hasattr(cls, key):
raise TypeError("%s() received an invalid keyword %r. as_view "
"only accepts arguments that are already "
"attributes of the class." % (cls.__name__, key))
def view(request, *args, **kwargs):
self = cls(**initkwargs)
if hasattr(self, 'get') and not hasattr(self, 'head'):
self.head = self.get
self.setup(request, *args, **kwargs)
if not hasattr(self, 'request'):
raise AttributeError(
"%s instance has no 'request' attribute. Did you override "
"setup() and forget to call super()?" % cls.__name__
)
return self.dispatch(request, *args, **kwargs)
view.view_class = cls
view.view_initkwargs = initkwargs
# take name and docstring from class
update_wrapper(view, cls, updated=())
# and possible attributes set by decorators
# like csrf_exempt from dispatch
update_wrapper(view, cls.dispatch, assigned=())
return view
It will thus return the view function that it constructs in the as_view() method. When the view() method is then called when you "trigger" the view, it will construct a View instance with the optional **initkwargs you passed to the as_view() method. This thus means that each HTTP request, will construct a new View object.
Next it will "setup" the obect by adding the request, the args and the kwargs to the instance. Finally it will call self.dispatch(..) this method will take a look at the request method (GET, POST, PUT, PATCH, DELETE, …), look if it is part of the acceptable methods, and in that case trigger the corresponding .get(..), .post(..), .put(..), … method, and return the result of that method.