在 Python 中实现装饰器模式 [英] Implementing the decorator pattern in Python

问题描述

我想在 Python 中实现 装饰模式，不知道有没有办法编写一个装饰器来实现它想要修改的函数，而不需要为所有刚刚转发给被装饰对象的函数编写样板文件.像这样:

I want to implement the decorator pattern in Python, and I wondered if there is a way to write a decorator that just implements the function it wants to modify, without writing boiler-plate for all the functions that are just forwarded to the decorated object. Like so:

class foo(object):
    def f1(self):
        print "original f1"
    def f2(self):
        print "original f2"

class foo_decorator(object):
    def __init__(self, decoratee):
        self._decoratee = decoratee
    def f1(self):
        print "decorated f1"
        self._decoratee.f1()
    def f2(self):              # I would like to leave that part out
        self._decoratee.f2()

我希望对 foo_decorator.f2 的调用自动转发到 decoratee.f2.有没有办法编写一个通用方法，将所有未实现的函数调用转发给 decoratee?

I would like to have calls to foo_decorator.f2 forwarded to decoratee.f2 automatically. Is there a way to write a generic method that forwards all unimplemented function-calls to decoratee?

推荐答案

你可以使用 __getattr__:

class foo(object):
    def f1(self):
        print "original f1"
    def f2(self):
        print "original f2"

class foo_decorator(object):
    def __init__(self, decoratee):
        self._decoratee = decoratee
    def f1(self):
        print "decorated f1"
        self._decoratee.f1()
    def __getattr__(self, name):
        return getattr(self._decoratee, name)

u = foo()
v = foo_decorator(u)
v.f1()
v.f2()

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