编辑“︁C++ 桥接模式”︁（章节）

=== 案例：跨平台图形渲染 ===
假设我们需要开发一个跨平台的图形渲染库，支持不同平台（Windows、Linux）和不同渲染API（OpenGL、Vulkan）。使用桥接模式可以避免为每个平台和API组合创建子类：

<syntaxhighlight lang="cpp">
// 实现类接口：渲染API
class RenderAPI {
public:
    virtual ~RenderAPI() = default;
    virtual void render() = 0;
};

// 具体实现类：OpenGL
class OpenGL : public RenderAPI {
public:
    void render() override {
        std::cout << "Rendering with OpenGL." << std::endl;
    }
};

// 具体实现类：Vulkan
class Vulkan : public RenderAPI {
public:
    void render() override {
        std::cout << "Rendering with Vulkan." << std::endl;
    }
};

// 抽象类：图形
class Graphic {
protected:
    RenderAPI* renderer;
public:
    Graphic(RenderAPI* renderer) : renderer(renderer) {}
    virtual ~Graphic() = default;
    virtual void draw() = 0;
};

// 扩展抽象类：圆形
class CircleGraphic : public Graphic {
public:
    CircleGraphic(RenderAPI* renderer) : Graphic(renderer) {}
    void draw() override {
        std::cout << "Drawing a circle: ";
        renderer->render();
    }
};

int main() {
    RenderAPI* opengl = new OpenGL();
    RenderAPI* vulkan = new Vulkan();

    Graphic* circle1 = new CircleGraphic(opengl);
    Graphic* circle2 = new CircleGraphic(vulkan);

    circle1->draw(); // 输出: Drawing a circle: Rendering with OpenGL.
    circle2->draw(); // 输出: Drawing a circle: Rendering with Vulkan.

    delete opengl;
    delete vulkan;
    delete circle1;
    delete circle2;

    return 0;
}
</syntaxhighlight>