decorator and the use of "self"

[xrfang]

I want to use decorator to control access to some page, e.g.:

class listing:
@login_required
def GET(self):
return "You are allowed to see the listing..."

there are 2 versions of decorators: a function and a class, the
function does not work, while the class worked.

question #1: what's wrong with this function:

def login_required(f, *args):
def new_f(*args):
if session.uid == 0:
raise web.seeother("/tasks/")
else:
f(*args)
return new_f

its problem is that if session.uid is not 0, the f(*args) call does
not work (GET is not called, and webpy display a bare "None" on the
page)

question #2: the following decorator worked:

class login_required:
def __init__(self, function):
self.function = function
def _do_login(self):
raise web.seeother("/tasks/")
def __call__(self):
if session.uid == 0:
return self._do_login()
else:
return self.function(self)

but I am confused about the use of "self": why _do_login() and function
(self)? if I use either _do_login(self) or function() there will be
errors. In another word, when the "self" is expected, and when is it
"injected" to method calls?

Thanks.

[xrfang]

question #1 is solved, I must write return f(*args) instead of f
(*args) alone. But #2 is still not solved. Also, I would like some
comment about what's the difference of using function or class as
decorators? is there any pros and cons of them?

Thanks

[Anand Chitipothu]

> question #1:  what's wrong with this function:
>
> def login_required(f, *args):
>    def new_f(*args):
>        if session.uid == 0:
>            raise web.seeother("/tasks/")
>        else:
>            f(*args)
>    return new_f
>
> its problem is that if session.uid is not 0, the f(*args) call does
> not work (GET is not called, and webpy display a bare "None" on the
> page)

because you are not returning anything from new_f. Change the else
part to "return f(*args)