First of all. Thanx for the help!!! The internet is just fantastic!!

I like the wrapper approach.

I had not thought of that approach myself. Sounds very reasonable. -So I started wrapping Resolver, but got stuck pretty fast. I get a problem saying that

'NoneType' object has no attribute 'addCallback'

"addCallback" seems to be implemented in defer.py, but im unsure on how to handle that in the wrapper?

Kind regards

/Tax

P.S:
As a side question: In my old hack approach, which I have had almost working, I have had problems constructing valid DNS answers. Wold you happen to know what requirements there is to the returning package, to be accepted.

I made some attempts by using pickle to capture live packages, but have a hard time tweaking other values than the address. Ideally I would like to pass on a very short TTL, so the client would not be bothered by fake DNS when I turn the system off.

As you might have guessed, Im building a gateway system for a small set of apartments. Requirements are:

invalid domains should go to a shop
valid domains should be redirected to the shop if the client have not paid, except if the query is for paypal.





2009/10/25 <exarkun@twistedmatrix.com>
On 24 Oct, 08:04 pm, jesper@taxboel.dk wrote:
>Im looking at the common.py and I feel a bit confused about how to wrap
>a
>resolver.
>
>Would'nt a subclass achieve the same thing. I would only need to
>implement
>the changed functions in the subclass.
>
>I guess my problem is that I dont exactly know how to write a wrapper
>in
>python.

There's nothing special to it.  Just do the obvious thing:

   class SomeWrapper:
       def __init__(self, wrapee):
           self.wrapee = wrapee

       def someMethod(self, args):
           do something with self.wrapee.someMethod and args

common.py will show you all the methods that a resolver is expected to
have.  Subclassing ResolverBase might help, though it's unfortunate that
it works by demultiplexing everything to "_lookup", a private method
that Twisted's compatibility policy doesn't guarantee will continue to
operate as it presently does.

Wrapping (ie "containment" or "has-a") is just an alternative
implementation strategy to subclassing (ie "inheritance" or "is-a").
Generally it's a better approach for various reasons, none of which are
really specific to Twisted.

Jean-Paul

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