Question

I’m trying to create an object collection proxy, which could do something like this:

class A:
    def do_something():
        # ...

class B:
    def get_a():
        return A()

class Proxy:
    ?

collection = [B(), B()]
proxy = Proxy(collection)

proxy.get_a().do_something()
# ^ for each B in collection get_a() and do_something()

What would be the best architecture / strategy for achieving this?

The key question, I guess is, how to cache the result of get_a() so I can then proxy do_something()

N.B. I don’t expect proxy.get_a().do_something() to return anything sensible, it’s only supposed to do things.

Answer 1

Simple enough… you may want to adapt it to do some more checking

class A(object):
    def do_something(self):
        print id(self), "called"

class B(object):
    def get_a(self):
        return A()

class Proxy(object):
    def __init__(self, objs):
        self._objs = objs

    def __getattr__(self, name):
        def func(*args, **kwargs):
            return Proxy([getattr(o, name)(*args, **kwargs) for o in self._objs])
        return func

collection = [B(), B()]

proxy = Proxy(collection)
proxy.get_a().do_something()

Results in:

4455571152 called
4455571216 called