python父类'包装'子类方法 [英] python parent class 'wrapping' child-class methods

问题描述

我的python代码中有以下情况：

I have the following situation in my python code:

class Parent(object):
    def run(self):
        print "preparing for run"
        self.runImpl()
        print "run done"

class Child(Parent):
    def runImpl(self):
        print "child running"

但是，我有几个这样的'装饰者'，在'runImpl'之前和之后做不同的设置/拆卸步骤，我不喜欢定义 run（）， runImpl（ ）， runImplSingleProcess（）等。

However, I have several such 'decorators', doing different setup/teardown steps before and after 'runImpl', and I don't like having to define run(), runImpl(), runImplSingleProcess() etc.

我正在寻找一个解决方案以下表格：

I am looking for a solution of the following form:

class Parent(object):
    @wrapping_child_call
    def run(self, func_impl, *args, **kwargs)
        print "preparing for run"
        func_impl(*args, **kwargs)
        print "run done"

class Child(Parent):
    def run(self):
        print "child running"

通过这种方式，Child类几乎不需要知道这种情况。

In this way, there is almost no need for Child class to be aware of this going on.

多重继承可能存在问题。如果 Child 继承自 Parent1 和 Parent2 ，我老实说不知道应该是什么样的正确行为。

There may also be an issue with multiple inheritance. If a Child inherits from Parent1 and Parent2, I honestly don't know what should be the correct behavior.

有没有人知道一种好的，自然的方式来实现这个目标？或者我在这里强调设计？

Does anyone know a good, natural, way of accomplishing this? or am I raping the design here?

谢谢

Yonatan

Thanks
Yonatan

推荐答案

不要在这里使用继承

反转你的设计。而不是一个is-a关系的父子实现，为什么不只是有一个组合，所以你得到一个有一个的关系？您可以定义实现您想要的方法的类，而您的上一个父类将使用这些特定于实现的类进行实例化。

Don't use inheritance here

Invert your design. Instead of a parent-child implementation which is a "is-a" relationship why not just have a composition so you get a "has-a" relationship? You could define classes which implement the methods you'd like while your previous parent class would be instantiated with those implementation specific classes.

class MyClass:
    def __init__(self, impl)
        self.impl = impl
    def run(self,var):
        print "prepare"
        impl.runImpl(var)
        print "I'm done"

class AnImplementation:
    def runImpl(self,var):

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