c++怎么实现一个装饰器(Decorator)设计模式_c++装饰器模式实现与应用

#include <iostream>
#include <string>

// 组件基类
class Widget {
public:
    virtual ~Widget() = default;
    virtual void draw() const = 0;
};

// 具体组件：基础文本框
class TextField : public Widget {
    std::string text;
public:
    explicit TextField(const std::string& t) : text(t) {}
    void draw() const override {
        std::cout << "Drawing text field with: '" << text << "'\n";
    }
};

// 装饰器基类
class WidgetDecorator : public Widget {
protected:
    Widget* widget;
public:
    explicit WidgetDecorator(Widget* w) : widget(w) {}
    void draw() const override {
        widget->draw(); // 默认转发调用
    }
};

// 添加边框的装饰器
class BorderDecorator : public WidgetDecorator {
public:
    explicit BorderDecorator(Widget* w) : WidgetDecorator(w) {}
    void draw() const override {
        WidgetDecorator::draw();
        std::cout << " + Adding border\n";
    }
};

// 添加滚动条的装饰器
class ScrollDecorator : public WidgetDecorator {
public:
    explicit ScrollDecorator(Widget* w) : WidgetDecorator(w) {}
    void draw() const override {
        std::cout << " + Adding scrollbars\n";
        WidgetDecorator::draw();
    }
};

int main() {
    // 创建原始组件
    Widget* input = new TextField("Hello");

    // 动态添加功能
    Widget* withBorder = new BorderDecorator(input);
    Widget* withScroll = new ScrollDecorator(withBorder);

    // 执行绘制
    withScroll->draw();

    // 注意：实际中应使用智能指针管理内存
    delete withScroll; // 会递归释放所有包装层

    return 0;
}

 + Adding scrollbars
Drawing text field with: 'Hello'
 + Adding border