AdaptionFailure: How to use Interfaces with PyProtocols ?

[Jay Parlar]

On Feb 10, 2006, at 4:21 AM, Nebur wrote:
> Hi,
> I tried to understand the docs of Peak's PyProtocols, and failed.
> I use PyProtocols v0.93 final. I fetched the ...tar.gz file for Linux
> and installed it using the setup.py.
> Here's my Hello-World-like example, that defines a Duck, which
> "implements" the given Interface:
>
>
>  from protocols import Interface,adapt,advise
>
>  class Quackable(Interface):
> 	 def quack(loudness):
> 		 """ print how loud to quack """
>  class Duck:
> 	 advise(instancesProvide=[Quackable,])
> 	 def quack(self, loudness):
> 		 print "quack! %s loud"%(loudness)
>
>  if __name__ == "__main__":
> 	 d = adapt(Duck, Quackable) # this line raises the failure
> 	 d.quack(3)
>

You've *almost* got it. The adaption adapts *instances* of a class. 
Your setup is correct, but change your __main__ to:

if __name__ == "__main__":
     d = Duck()
     adapted_d = adapt(d, Quackable)
     adapted_d.quack(3)


or more concisely:

if __name__ == "__main__":
     d = adapt(Duck(), Quackable)
     d.quack(3)

Of course, it's kind of a pointless example, because you're adapting 
something that declares to be Quackable to a Quackable object, but I'm 
sure you know that :)

Most of my own work with PyProtocols would not involve objects that 
just had 'instancesProvide', but would also have 'asAdapterFor' (at 
least, I think it's 'asAdapterFor', it's been a few months since I've 
touched my PyProtocols related code)

Jay P.