C++接口定义与实现方法

class Drawable {
public:
    virtual ~Drawable() = default;                // 虚析构函数
    virtual void draw() const = 0;               // 纯虚函数
    virtual void resize(float scale) = 0;
};

class Circle : public Drawable {
private:
    float radius;
public:
    Circle(float r) : radius(r) {}

    void draw() const override {
        std::cout << "Drawing a circle with radius " << radius << "\n";
    }

    void resize(float scale) override {
        radius *= scale;
    }
};

class Rectangle : public Drawable {
private:
    float width, height;
public:
    Rectangle(float w, float h) : width(w), height(h) {}

    void draw() const override {
        std::cout << "Drawing a rectangle " << width << "x" << height << "\n";
    }

    void resize(float scale) override {
        width *= scale;
        height *= scale;
    }
};

void render(const Drawable& obj) {
    obj.draw();
}

int main() {
    Circle c(5.0f);
    Rectangle r(3.0f, 4.0f);

    render(c);  // 输出: Drawing a circle...
    render(r);  // 输出: Drawing a rectangle...

    return 0;
}