C++ 函数的虚函数是如何声明和使用的

class Base {
public:
    virtual void print() const {
        cout << "Base::print()" << endl;
    }
};

int main() {
    Base* basePtr = new Derived;  // 指向 Derived 对象的基类指针
    basePtr->print();  // 实际调用 Derived::print()
    return 0;
}

class Shape {
public:
    virtual double getArea() const = 0;  // 纯虚函数
};

class Rectangle : public Shape {
public:
    double width, height;
    Rectangle(double w, double h) : width(w), height(h) {}
    double getArea() const override { return width * height; }
};

class Circle : public Shape {
public:
    double radius;
    Circle(double r) : radius(r) {}
    double getArea() const override { return M_PI * radius * radius; }
};

int main() {
    Shape* shapes[] = { new Rectangle(2, 3), new Circle(4) };
    double totalArea = 0;
    for (auto shape : shapes) {
        totalArea += shape->getArea();
    }
    cout << "Total Area: " << totalArea << endl;
    return 0;
}

Total Area: 28.2743