使用纯虚拟函数绕圈子

class Base {
public:
    virtual void pureVirtualFunction() = 0; // 纯虚函数声明
};

class Derived : public Base {
public:
    void pureVirtualFunction() override {
        // 实现纯虚函数
    }
};

// 抽象基类
class Shape {
public:
    virtual double area() const = 0; // 纯虚函数
    virtual ~Shape() = default;
};

// 派生类
class Circle : public Shape {
public:
    Circle(double radius) : radius_(radius) {}
    double area() const override {
        return 3.14 * radius_ * radius_;
    }
private:
    double radius_;
};

// 使用示例
int main() {
    std::unique_ptr<Shape> shape = std::make_unique<Circle>(5.0);
    std::cout << "Area: " << shape->area() << std::endl;
    return 0;
}