python-3.x - Python 设计模式 : Nested Abstract Classes

Question

在下面的示例代码中，我想要每个 car要组成的对象 brake_system和 engine_system对象，它们作为属性存储在汽车上。

为了实现这一点，我定义了 Car , BreakSystem和 EngineSystem作为抽象类。 Car的每个子类需要定义其各自的 BreakSystem和 EngineSystem子类作为类属性。

这种方法有什么潜在的问题吗？或者还有其他更适合处理嵌套抽象的设计模式吗？

from abc import ABC, abstractmethod

class Car(ABC):
    """
    every car object should have an Engine object and a BrakeSystem object
    """

    def __init__(self):
        self.engine_system = self._engine_type()
        self.brake_system = self._brake_type()

    @property
    @abstractmethod
    def _engine_type(self):
        raise NotImplementedError()

    @property
    @abstractmethod
    def _brake_type(self):
        raise NotImplementedError()

class EngineSystem(ABC):
    pass

class BrakeSystem(ABC):
    pass


class FooBrakeSystem(BrakeSystem):
    pass

class FooEngineSystem(EngineSystem):
    pass

class FooCar(Car):
    _engine_type = FooEngineSystem
    _brake_type = FooBrakeSystem

if __name__ == '__main__':
    obj = FooCar()

Answer 1

I want every car object to be composed of brake_system and engine_system objects

你有系统的抽象类

class EngineSystem(ABC):
    pass

class BrakeSystem(ABC):
    pass

一辆汽车必须由两个系统组成:

class Car:

    def __init__(self, engine: EngineSystem, brake: BrakeSystem):
        self._engine_system = engine
        self._brake_system = brake

    @property
    def engine_type(self) -> EngineSystem:
        return self._engine_system

    @property
    def brake_type(self) -> BrakeSystem:
        return self._engine_system

现在，如果您需要创建特定的汽车

tesla = Car(ElectroEngine(), Disks())

# or even 
class Tesla(Car):
    def __init__(self):
        super().__init__(ElectroEngine(), Disks())

tesla = Tesla()

这种方法允许您创建一个 car作为其系统的组合。