python - 通知父实例有关属性更改

Question

我有这两个类:

class Status(object):
    def __init__(self):
        self._message = ''

    @property
    def message(self):
        return self._message

    @message.setter
    def message(self, value):
        self._message = value


class Buddy(object):
    def __init__(self, name):
        self.name = name
        self.status = Status()

    def status_updated(self):
        # this should be called when self.status.message is changed

我这样使用它们:

buddy = Buddy('John')
buddy.status.message = 'Hello world!'  # this should call Buddy.status_updated

我希望在修改 Status 的 message 属性时调用 Buddy.status_updated。如何实现？

Answer 1

您必须将引用存储返回给父级； python 值不跟踪它们的存储位置(可以有多个位置引用您的 Status() 实例):

class Status(object):
    def __init__(self, parent=None):
        self._message = ''
        self._parent = parent

    @property
    def message(self):
        return self._message

    @message.setter
    def message(self, value):
        self._message = value
        if self._parent is not None:
            self._parent.status_updated()


class Buddy(object):
    def __init__(self, name):
        self.name = name
        self.status = Status(self)

    def status_updated(self):
        # this should be called when self.status.message is changed