Glyph Lefkowitz a écrit :
> On Nov 24, 2009, at 4:26 PM, Olivier Parisy wrote:
>
>
>> Is this the "twisted" way to analyse this? Or should I use some kind of
>> "proxy" DatagramProtocol which would relay datagramReceived calls to the
>> proper DatagramProtocol, depending on the current protocol state
>> (handshaking or data exchange)?
>>
>
> Currently, the right way to do this is to do as you suggest, and have two
> DatagramProtocol instances, and a third which switches between them.
>
I tried to implement such a "switching" class so that I could freely
change the DatagramProtocol handling a given port without releasing it.
It is typically used in the following way :
self.protocol =
DelegatingDatagramProtocol(MyFirstDatagramProtocol())
self.udpPort = reactor.listenUDP(0, self.protocol)
Then, later in the code :
self.protocol.switchProtocol(MySecondDatagramProtocol())
Here is my current implementation :
# Breaks when inheriting from DatagramProtocol?
class DelegatingDatagramProtocol:
def __init__(self, protocol):
self._protocol = protocol
def switchProtocol(self, protocol):
self._protocol = protocol
protocol.transport = self.transport
def makeConnection(self, transport):
self._protocol.makeConnection(transport)
# Needed by switchProtocol
self.transport = transport
# Avoid an AssertionError (protocol.py:527 assert self.numPorts > 0)
def doStop(self):
pass
# See
http://www.python.org/workshops/1997-10/proceedings/savikko.html (Proxy
pattern)
def __getattr__(self, name):
print 'Delegating to protocol: %s' % name
return getattr(self._protocol, name)
It mostly works, but I have two issues with it :
- When doStop() is called by the reactor, an AssertionError is raised. I
suppose this is due to my "sharing" of the transport in switchProtocol
(which ensures that "transport.write" calls are directed to the proper
transport), but how can I fix it?
- If my class extends DatagramProtocol, it stops working
(transport.write calls seems honored, then nothing works... I suppose
datagramReceived is never called). Why is it so?
Regards,
Olivier.
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