#3783. [GESP202503 六级 C++] 第 15 题

[GESP202503 六级 C++] 第 15 题

关于下面代码,说法错误的是( )。

class Shape {
protected:
    string name;

public:
    Shape(const string& n) : name(n) {}

    virtual double area() const {
        return 0.0;
    }
};

class Circle : public Shape {
private:
    double radius; // 半径

public:
    Circle(const string& n, double r) : Shape(n), radius(r) {}

    double area() const override {
        return 3.14159 * radius * radius;
    }
};

class Rectangle : public Shape {
private:
    double width;   // 宽度
    double height; // 高度

public:
    Rectangle(const string& n, double w, double h) : Shape(n), width(w), height(h)
    {}

    double area() const override {
        return width * height;
    }
};

int main() {
    Circle circle("MyCircle", 5.0);
    Rectangle rectangle("MyRectangle", 4.0, 6.0);

    Shape* shapePtr = &circle;
    cout << "Area: " << shapePtr->area() << endl;

    shapePtr = &rectangle;
    cout << "Area: " << shapePtr->area() << endl;

    return 0;
}

{{ select(1) }}

  • 语句 Shape* shapePtr = &circle;shapePtr = &rectangle; 出现编译错误
  • Shape 为基类,CircleRectangle 是派生类
  • 通过继承,CircleRectangle 复用了 Shape 的属性和方法,并扩展了新的功能
  • CircleRectangle 通过重写(override)基类的虚函数 area 和基类指针,实现了运行时多态