虚函数基本概念

class Animal {
public:
    virtual void makeSound() {
        std::cout << "The animal makes a sound." << std::endl;
    }
};
class Dog : public Animal {
public:
    void makeSound() override {
        std::cout << "The dog barks." << std::endl;
    }
};
class Cat : public Animal {
public:
    void makeSound() override {
        std::cout << "The cat meows." << std::endl;
    }
};

Animal* animal = new Dog();
animal->makeSound();  // Output: "The dog barks."

animal = new Cat();
animal->makeSound();  // Output: "The cat meows."

• 上面两块代码中Animal 的makeSound()是作为虚函数存在。虚函数允许子类（派生类）对其进行重写（override），从而实现多态性。。在 Animal 类中，makeSound() 函数的默认行为是输出一条消息 "The animal makes a sound."。子类可以对 makeSound() 进行重写，以实现特定的行为。