Proof of concept for tying a metaclass auto-decorator with a service bus

metaclass_servicebus.py

from collections import defaultdict
from functools import wraps
decoratedCalls = defaultdict(list)

def call(name, *args, **kwargs):
    print name, args, kwargs
    if name in decoratedCalls:
        for cb in decoratedCalls[name]:
            cb(*args, **kwargs)

class Subscribe(object):
    def __init__(self, name):
        self.name = name
        
    def __call__(self, f):
        decoratedCalls[self.name].append(f)
        return f
        


class BusDecorator(object):
    def __init__(self, name):
        self.name = name
        
    def __call__(self, f):
        
        @wraps(f)
        def decorator(inst, *args, **kwargs):
            call("%s-pre" % self.name, inst, args, kwargs)            
            retval = f(inst, *args, **kwargs)
            call("%s-post" % self.name, inst, retval)            
            return retval
        return decorator

class BusWrap(type):
    
    def __new__(mcs, clsname, bases, cdict):
        dbg = 1
        modName = cdict.get("__module__", "unknownclass")
        
        for name in cdict.keys():
            prefix = "%s.%s.%s" % ( modName, clsname, name)
            if callable(cdict[name]):                
                cdict[name] = BusDecorator(prefix)(cdict[name])
        
        return type.__new__(mcs, name, bases, cdict)
        

            
class Foo(object):
    __metaclass__ = BusWrap
    
    def __init__(self):
        print "init'd"
        
    def bar(self):
        print "bar"
        
    def blah(self):
        print "blah"
        
    def ich(self):
        print "ich"
        
    def ego(self):
        print "lego"
        
    def say(self, *args):
        print "Saying ", args
        

@Subscribe("__main__.Foo.bar-pre")        
def preBar(inst, *args, **kwargs):
    if not hasattr(inst, "ext_info"):
        inst.ext_info = "Here"
        
@Subscribe("__main__.Foo.ego-post")
def postEgo(inst, *args, **kwargs):
    if hasattr(inst, "ext_info"):
        print "Extended info is ", inst.ext_info

x = Foo()
x.bar()
x.blah()
x.ich()
x.ego()
x.say("abba", "dabba")

dbg = 1