在Python中可以实现mixin行为而不使用继承吗？ [英] In Python can one implement mixin behavior without using inheritance?

问题描述

在Python中是否有合理的方法来实现类似于Ruby中的mixin行为 - 也就是说，不使用继承？

Is there a reasonable way in Python to implement mixin behavior similar to that found in Ruby -- that is, without using inheritance?

class Mixin(object):
    def b(self): print "b()"
    def c(self): print "c()"

class Foo(object):
    # Somehow mix in the behavior of the Mixin class,
    # so that all of the methods below will run and
    # the issubclass() test will be False.

    def a(self): print "a()"

f = Foo()
f.a()
f.b()
f.c()
print issubclass(Foo, Mixin)

我有一个模糊的想法这是一个类装饰，但我的尝试导致混乱。我对该主题的大多数搜索都指向了使用继承（或者在更复杂的场景中，多重继承）以实现mixin行为。

I had a vague idea to do this with a class decorator, but my attempts led to confusion. Most of my searches on the topic have led in the direction of using inheritance (or in more complex scenarios, multiple inheritance) to achieve mixin behavior.

推荐答案

def mixer(*args):
    """Decorator for mixing mixins"""
    def inner(cls):
        for a,k in ((a,k) for a in args for k,v in vars(a).items() if callable(v)):
            setattr(cls, k, getattr(a, k).im_func)
        return cls
    return inner

class Mixin(object):
    def b(self): print "b()"
    def c(self): print "c()"

class Mixin2(object):
    def d(self): print "d()"
    def e(self): print "e()"


@mixer(Mixin, Mixin2)
class Foo(object):
    # Somehow mix in the behavior of the Mixin class,
    # so that all of the methods below will run and
    # the issubclass() test will be False.

    def a(self): print "a()"

f = Foo()
f.a()
f.b()
f.c()
f.d()
f.e()
print issubclass(Foo, Mixin)

输出：

a()
b()
c()
d()
e()
False

这篇关于在Python中可以实现mixin行为而不使用继承吗？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！