如何在C++中实现工厂设计模式？

// 抽象工厂
class ShapeFactory {
public:
    virtual Shape* createShape() = 0;
};

// 具体工厂（创建圆形）
class CircleFactory : public ShapeFactory {
public:
    Shape* createShape() override {
        return new Circle;
    }
};

// 具体工厂（创建方形）
class SquareFactory : public ShapeFactory {
public:
    Shape* createShape() override {
        return new Square;
    }
};

// 产品（形状）
class Shape {
public:
    virtual void draw() = 0;
};

// 具体产品（圆形）
class Circle : public Shape {
public:
    void draw() override {
        cout << "Drawing a circle..." << endl;
    }
};

// 具体产品（方形）
class Square : public Shape {
public:
    void draw() override {
        cout << "Drawing a square..." << endl;
    }
};

// 调用者
void drawShapes(ShapeFactory* factory) {
    Shape* shape = factory->createShape();
    shape->draw();
    delete shape;
}

int main() {
    CircleFactory circleFactory;
    SquareFactory squareFactory;

    drawShapes(&circleFactory);
    drawShapes(&squareFactory);

    return 0;
}