python - 基于多态性的函数返回 None

Question

我一直在尝试测试 Python 中的多态性 由于某种原因，我的函数返回 None 。 你能从下面的代码中看出原因吗？提前致谢

class Animal:
    __name = ""
    __height = 0
    __weight = 0
    __sound = 0

    def __init__(self, name, height, weight, sound):
        self.__name = name
        self.__height = height
        self.__weight = weight
        self.__sound = sound

    def set_name(self, name):
        self.__name = name

    def get_name(self):
        return self.__name

    def get_sound(self):
        return self.__sound

    def toString(self):
        return "{} is {} cm tall {} kg and says {}".format(self.__name, self.__height, self.__weight, self.__sound)

cat = Animal("Whiskers", 33, 10, "Meow")

-- 狗类:

class Dog(Animal):
    __owner = ""

    def __init__(self, name, height, weight, sound, owner):
        self.__owner = owner
        super(Dog, self).__init__(name, height, weight, sound)

    def set_owner(self, owner):
        self.__owner = owner

    def get_owner(self):
        return self.__owner

    def get_sound(self):
        return "Woff!"

    def toString(self):
        return "Overriden"

shnitzel = Dog("Shnitzel", 10, 15, 0, "CodingCode")

测试类:

class AnimalTesting:
    def get_sound(self, animal):
        animal.get_sound()

    test_animals = AnimalTesting()
    print test_animals.get_sound(cat)

该行:print test_animals.get_sound(cat) 返回无 再次感谢大家!

Answer 1

我认为这非常简单，与多态性无关。您只是忘记了返回:

class AnimalTesting:
    def get_sound(self, animal):
        return animal.get_sound()