[EMAIL PROTECTED] wrote:
> I'm developing a library at the moment that involves many classes, some
> of which have "exposed" capabilities. I'm trying to design a nice
> interface for both exposing those capabilities, and inspecting
> instances to find out what capabilities they have.
>
> At the moment, I'm leaning towards a superclass (Exposed) that defines
> a static method which is a decorator (expose) such that any derived
> class can mark a method with @Exposed.expose and it will then be later
> returned by getExposedMethods(), a la:
>
> class Exposed:
> @staticmethod
> def expose( f ):
> ...
>
> def getExposedMethods( self ):
> ...
>
> class Person( Exposed ):
> @Exposed.expose
> def talk( self, ... ):
> ...
>
> I'm trying to implement the decorator by having it populate a static
> member list of whatever class it's in with a reference to the method.
> getExposedMethods() would then return the contents of each of those
> lists from itself back to Exposed in the class hierarchy. The first
> problem was that having a reference to the method (i.e. talk()) does
> not allow you to get a reference to the enclosing class (I had hoped
> im_class would lead me there).
Not yet. When your decorator is called, the class object is not yet
created, and what you are decorating is a plain function.
> The real hiccup was that explicitly
> passing the class as an argument to the decorator generates a undefined
> global name error, presumably because at that point of execution the
> class object hasn't been fully created/initialised.
Exactly.
> So how can this be done?
The simplest thing is to use a two-stages scheme : mark the functions as
exposed, then collect them:
def expose(func):
func._exposed = True
return func
def exposed(obj):
return callable(obj) and getattr(obj, '_exposed', False)
class Exposing(object):
@classmethod
def get_exposed_methods(cls):
try:
exposeds = cls._exposed_methods
except AttributeError:
exposeds = []
for name in dir(cls):
obj = getattr(cls, name)
if exposed(obj):
exposeds.append(obj)
cls._exposed_methods = exposeds
return exposeds
class Parrot(Exposing):
@expose
def parrot(self, what):
return "%s says %s" % (self, str(what))
HTH
--
bruno desthuilliers
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])"
--
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