问题描述
我想知道是否可能，如果可以，在实现组合时如何访问超级"类实例的属性.
I would like to know if it's possible, and if yes, how to access attribute(s) of a "super" class instance, when having composition implemented.
下面提供的示例仅是为了在此处提供想法，并为进一步的说明建立共识.
Example provided below is only to provide idea here and setup common ground on further explanations.
我想直接从对象门"(类型DoorElement)访问MiniVan实例的"id"属性.
I want to have access to "id" attribute for an instance of MiniVan directly from object "door" (type DoorElement).
我的代码
class Car:
def __init__(self, _id):
self.id = _id
class CarElement:
def __init__(self, name):
self.name = name
def get_car_id(self):
# Body which will access value of attribute "id"
return car_id
class MiniVan(Car):
def __init__(self, _id):
super(MiniVan, self).__init__(_id)
self.door = DoorElement('door')
self.engine = EngineElement('engine')
class DoorElement(CarElement):
def __init__(self, name):
super(DoorElement, self).__init__(name)
class EngineElement(CarElement):
def __init__(self, name):
super(EngineElement, self).__init__(name)
def main():
mini_van = MiniVan(123)
id_from_door = mini_van.door.get_car_id()
id_from_engine = mini_van.engine.get_car_id()
print(id_from_door) # Expected output 123
print(id_from_engine) # Expected output 123
if __name__ == '__main__':
main()
预期:
- 打印两次"123"
我尝试过的事情:
- 在创建对象时传递必需的属性
我知道我可以通过传递"car_id"来定义 init 方法，但是出于某些原因，我希望尽可能避免使用它.如果没有的话，我可能会去做.
I know that I could just define init method with passing "car_id" but for some reasons I would love to avoid it if possible. If not, I would propably just go for it.
- 设置类属性，然后在类方法中从CarElement类调用它，例如:
- to set class attribute, and then call it from CarElement class within classmethod e.g.:
@classmethod
def get_id(cls):
return Car.id
但是这种解决方案的问题在于，我可以为Car类设置许多子类(MiniVan，Truck等)，并且希望它仍然可以正常工作.
But issue with this solution is that, I can have many child-classes for Car class (MiniVan, Truck, etc.) and I want have it still working.
- 尝试使用描述符
def __get__(self, instance, owner):
return instance.id
但是我可以理解为错误，实际上getter(据我了解干净的代码)应该返回类的实例，而不是任何属性.
But I could understand it wrong, and actually getter (as far as I understand clean code) should return instance of a class and not any attribute.
其他信息
- 我将始终使用CarElement(或子类)实例作为Car(或子类)实例的实例的属性-不同的用法将被视为使用错误
- Car类可以有很多不同的子类，但总是在继承方式内(Car<-RacingCar(Car)<-FormulaOneCar(RacingCar))但没有组成
推荐答案
为使代码正常工作，您必须使用 car_id 初始化所有 CarElement -s.当前，您遇到的错误是由于方法范围内缺少此类变量而引起的.我的更改想法是这样的:
In order for your code to work, you would have to initialize all CarElement-s with car_id. Currently, the error you are getting comes from lack of such a variable in the scope of the method. My idea of a change is this:
class CarElement:
def __init__(self, name, car_id):
self.name = name
self.car_id = car_id
def get_car_id(self):
# Body which will access value of attribute id
return self.car_id
我看不到其他任何魔术方式.
I can't see any other magic way.
这篇关于如何从另一个对象的方法(这是Python中的属性之一)访问对象的属性?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！