在子类中访问超类的属性设置器 [英] Access superclass' property setter in subclass

问题描述

我有一个SuperClass，它定义了一个属性和它的设置方法，就像这样:

I have a SuperClass which defines a property and it's setter, like so:

class A(object):
    def __init__(self):
        self._mode = None

    @property
    def mode(self):
        # to be overriden in subclass to implement the actual getter code
        raise NotImplementedError

    @mode.setter
    def mode(self, value):
        # common assertions and input validations
        self._set_mode(value)

    def _set_mode(self, value):
        # to be overriden in subclass to implement the actual setter code
        raise NotImplementedError


class B(A):
    @property
    def mode(self):
        return self._mode

    def _set_mode(self, value):
        self._mode = value


obj = B()
obj.mode = 'test'

哪个加薪

obj.mode = 'test'
AttributeError: can't set attribute

似乎我必须在B中注册一个二传手.我通常会像@A.mode.setter这样进行操作，但这在这里并不适用，因为我实际上不想在B中定义新的二传手，只需重复使用A中的一个即可.
有没有人暗示如何解决这个问题?可能微不足道，但我现在没有看到它:/

It would seem that I have to register a setter in B. I'd usually do this like @A.mode.setter, but that doesn't quite apply here as I don't actually want to define a new setter in B, just re-use the one from A.
Does anyone have a hint on how to solve this? Might be trivial, but I'm not seeing it right now :/

推荐答案

getter和setter被存储为property对象的属性(分别为.fget和.fset)，因此一旦您重载了子类中的属性，您最明确地提供了getter和setter，即:

the getter and setter are stored as attributes of the property object (respectively as .fget and .fset), so as soon as you overload the property in a child class you most explicitely provide both getter and setters, ie:

class B(A):
    @property
    def mode(self):
        return self._mode

    @mode.setter
    def mode(self, value):
        self._mode = value

因此，如果要使getter和/或setter可重载而不必重新声明该属性，则必须定义一个_get_mode方法，并使属性的getter委托对此方法进行操作，就像对setter所做的那样.

So if you want to make the getter and/or setter overloadable without having to redeclare the property, you have to define a _get_mode method and make your property's getter delegate to this method, just like you did for the setter.

class A(object):
    def __init__(self):
        self._mode = None

    @property
    def mode(self):
        return self._get_mode()

    def _get_mode(self):
        # to be overriden in subclass to implement the actual getter code
        raise NotImplementedError

    @mode.setter
    def mode(self, value):
        # common assertions and input validations
        self._set_mode(value)

    def _set_mode(self, value):
        # to be overriden in subclass to implement the actual setter code
        raise NotImplementedError


class B(A):

    def _get_mode(self):
        return self._mode

    def _set_mode(self, value):
        self._mode = value

这篇关于在子类中访问超类的属性设置器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！