编写一个工厂模式的样例，假设基类为Shape类，派生类为Cirdle(圆)和Rectangular (形)，方法为GetShapeName, 要求过基类对象调用派生类的方法

下面是一个工厂模式的示例，其中基类为Shape类，派生类为Circle(圆)和Rectangular(矩形)，方法为GetShapeName。

#include <iostream>
#include <string>

using namespace std;

// 基类 Shape
class Shape {
public:
    virtual string GetShapeName() = 0;
    virtual ~Shape() {}
};

// 派生类 Circle
class Circle : public Shape {
public:
    string GetShapeName() override {
        return "Circle";
    }
};

// 派生类 Rectangular
class Rectangular : public Shape {
public:
    string GetShapeName() override {
        return "Rectangular";
    }
};

// 工厂类 ShapeFactory
class ShapeFactory {
public:
    static Shape* CreateShape(string type) {
        if (type == "Circle") {
            return new Circle();
        } else if (type == "Rectangular") {
            return new Rectangular();
        }
        return nullptr;
    }
};

int main() {
    Shape* shape1 = ShapeFactory::CreateShape("Circle");
    Shape* shape2 = ShapeFactory::CreateShape("Rectangular");

    cout << shape1->GetShapeName() << endl; // 输出：Circle
    cout << shape2->GetShapeName() << endl; // 输出：Rectangular

    delete shape1;
    delete shape2;

    return 0;
}

在上面的示例中，我们定义了基类 Shape 和两个派生类 Circle 和 Rectangular。工厂类 ShapeFactory 可以创建 Circle 和 Rectangular 对象。我们可以使用基类 Shape 的指针来调用派生类的 GetShapeName() 方法。