Replace classmethod with descriptor

gistfile1.diff

diff --git a/django/views/generic/base.py b/django/views/generic/base.py
--- a/django/views/generic/base.py
+++ b/django/views/generic/base.py
@@ -9,6 +9,39 @@
 logger = getLogger('django.request')
 
 
+class AsViewDescriptor(object):
+    def __get__(self, instance, cls):
+        if instance is not None:
+            raise TypeError(u"You tried to call 'as_view()' on a View instance "
+                            u"instead of a View (sub)class")
+        def as_view(*initargs, **initkwargs):
+            """
+            Main entry point for a request-response process.
+            """
+            # sanitize keyword arguments
+            for key in initkwargs:
+                if key in cls.method_names:
+                    raise TypeError(u"You tried to pass in the %s method name as a "
+                                    u"keyword argument to %s(). Don't do that."
+                                    % (key, cls.__name__))
+                if not hasattr(cls, key):
+                    raise TypeError(u"%s() received an invalid keyword %r" % (
+                        cls.__name__, key))
+
+            def view(request, *args, **kwargs):
+                self = cls(*initargs, **initkwargs)
+                return self.dispatch(request, *args, **kwargs)
+
+            # 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
+        return as_view
+
+
 class View(object):
     """
     Intentionally simple parent class for all views. Only implements
@@ -17,6 +50,8 @@
 
     method_names = ['get', 'post', 'put', 'delete', 'head', 'options', 'trace']
 
+    as_view = AsViewDescriptor()
+
     def __init__(self, *args, **kwargs):
         """
         Constructor. Called in the URLconf; can contain helpful extra
@@ -27,33 +62,6 @@
         for key, value in kwargs.iteritems():
             setattr(self, key, value)
 
-    @classmethod
-    def as_view(cls, *initargs, **initkwargs):
-        """
-        Main entry point for a request-response process.
-        """
-        # sanitize keyword arguments
-        for key in initkwargs:
-            if key in cls.method_names:
-                raise TypeError(u"You tried to pass in the %s method name as a "
-                                u"keyword argument to %s(). Don't do that."
-                                % (key, cls.__name__))
-            if not hasattr(cls, key):
-                raise TypeError(u"%s() received an invalid keyword %r" % (
-                    cls.__name__, key))
-
-        def view(request, *args, **kwargs):
-            self = cls(*initargs, **initkwargs)
-            return self.dispatch(request, *args, **kwargs)
-
-        # 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
-
     def dispatch(self, request, *args, **kwargs):
         # Try to dispatch to the right method for that; if it doesn't exist,
         # raise a big error.
diff --git a/tests/regressiontests/generic_views/base.py b/tests/regressiontests/generic_views/base.py
--- a/tests/regressiontests/generic_views/base.py
+++ b/tests/regressiontests/generic_views/base.py
@@ -82,6 +82,12 @@
             self.rf.get('/', REQUEST_METHOD='FAKE')
         ).status_code, 405)
 
+    def test_instance_as_view(self):
+        """
+        Test that 'as_view' can be called only from a View class, not instance.
+        """
+        self.assertRaises(TypeError, getattr, CustomizableView(parameter="value"), "as_view")
+
     def test_invalid_keyword_argument(self):
         """
         Test that view arguments must be predefined on the class and can't