定义接口并使用接口的多个实现

Question

我无法理解以下要求的实现：

1. 创建一个接口类Interface。
2. 创建 n 个类 ImplementationN，以不同方式实现 Interface。
3. 创建一个新类 UsingInterface，它使用来自 Interface 的函数来定义自己的函数。
4. 创建 n 个新类，允许使用在 UsingInterface 中创建的函数，但通过 ImplementationN 类之一实现 UsingInteface 的方法使用的函数。

以下是我想出的解决方案：

Answer 1

在线解释。解决方案中的一个关键是将UsingInterface 设置为metaclass=ABCMeta，因此它（在本例中为IDE）不需要实现func1。

from abc import ABCMeta, abstractmethod


class Interface(object, metaclass=ABCMeta):
    """Class that defines an interface."""
    @abstractmethod
    def func1(self):
        pass


class Implementation1(Interface):
    """Class that implements the interface one way."""
    def func1(self):
        print('func1 was implemented here')


class Implementation2(Interface):
    """Class that implements the interface another way, differently."""
    def func1(self):
        print('func1 was implemented here as well, but differently')


class UsingInterface(Interface,  metaclass=ABCMeta):
    """Class that uses the interface to implement its own functions.
    `func1` is not implemented here, hence this has to be an `ABCMeta` class.
    Later, the correct implementation of `func1` based on the inherited
    Implementation class shall be used.

    We're inheriting `Interface`, so the IDE can tell us which methods
    we can call (in this case `self.func1()`).
    """
    def func2(self):
        print("I'm running func1 from the Interface: ")
        self.func1()


class Usage1(UsingInterface, Implementation1):
    pass    


class Usage2(UsingInterface, Implementation2):
    pass

u1 = Usage1()
u1.func2()
# I'm running func1 from the Interface:
# func1 was implemented here

u2 = Usage2()
u2.func2()
# I'm running func1 from the Interface:
# func1 was implemented here as well, but differently