C++如何实现抽象接口调用多种子类对象

class Shape {
public:
    virtual ~Shape() = default;                     // 虚析构函数
    virtual double area() const = 0;               // 纯虚函数
    virtual void draw() const = 0;                 // 纯虚函数
};

class Circle : public Shape {
    double radius;
public:
    Circle(double r) : radius(r) {}
    double area() const override {
        return 3.14159 * radius * radius;
    }
    void draw() const override {
        std::cout << "Drawing a circle\n";
    }
};
<p>class Rectangle : public Shape {
double width, height;
public:
Rectangle(double w, double h) : width(w), height(h) {}
double area() const override {
return width * height;
}
void draw() const override {
std::cout << "Drawing a rectangle\n";
}
};</p>

#include <vector>
#include <memory>
<p>int main() {
std::vector<std::unique_ptr<Shape>> shapes;
shapes.push_back(std::make_unique<Circle>(5.0));
shapes.push_back(std::make_unique<Rectangle>(4.0, 6.0));</p><pre class='brush:php;toolbar:false;'>for (const auto& shape : shapes) {
    std::cout << "Area: " << shape->area() << "\n";
    shape->draw();
}
return 0;

Area: 78.5398
Drawing a circle
Area: 24
Drawing a rectangle