python - 需要在 python 类中路由实例调用

Question

问题是在选择响应者之前需要考虑参数。到目前为止，这是我的尝试。

from responders import A, B, C

class RandomResponder(object)
    def init(self, *args, *kwargs):
        self.args = args
        self.kwargs = kwargs

    def __getattr__(self, name):
        # pick a responder based on the args the function was called with
        # I don't know how to do this part
        # for sake of argument lets the args a function was called with lead me to pick responder A
        r = A
        responder = r(*self.args, **self.kwargs)
        return responder.__getattr__(name)

期望的效果是:

r = RandomResponder()
r.doSomething(1)
#returns A.doSomething()
r.doSomething(2)
#returns B.doSomething()
r.doSomething(3)
#return C.doSomething()
r.doSomethingElse(1)
#returns A.doSomethingElse()
r.doSomethingElse(2)
#returns B.doSomethingElse()
r.doSomethingElse(3)
#returns C.doSomethingElse()

我不会提前知道响应器 A、B 和 C 包含的所有功能。

Answer 1

当你这样做的时候

r.doSomething(1)

按顺序发生的事情是:

• r.__getattr__ 被调用，并返回一个对象
• 使用参数“1”调用此对象

在调用 __getattr__ 时，您无法知道您返回的对象将用什么参数来调用，或者即使它会完全被调用...

因此，要获得您想要的行为，__getattr__ 必须返回一个可调用对象，该对象根据它调用时使用的参数自行做出决定。例如

from responders import A, B, C

class RandomResponder(object):
    def __getattr__(self, name):
        def func(*args, **kwds):
            resp = { 1:A, 2:B, 3:C }[args[0]]    # Decide which responder to use (example)
            return getattr(resp, name)()         # Call the function on the responder
        return func