C++如何实现装饰器模式 C++装饰器模式的应用

#include <iostream>
#include <string>

// 抽象组件类
class Component {
public:
    virtual std::string operation() = 0;
    virtual ~Component() {}
};

// 具体组件类
class ConcreteComponent : public Component {
public:
    std::string operation() override {
        return "ConcreteComponent";
    }
};

// 抽象装饰器类
class Decorator : public Component {
protected:
    Component* component;

public:
    Decorator(Component* component) : component(component) {}

    std::string operation() override {
        return component->operation();
    }
    virtual ~Decorator() {
        delete component;
    }
};

// 具体装饰器类 1
class ConcreteDecoratorA : public Decorator {
public:
    ConcreteDecoratorA(Component* component) : Decorator(component) {}

    std::string operation() override {
        return "ConcreteDecoratorA(" + Decorator::operation() + ")";
    }
};

// 具体装饰器类 2
class ConcreteDecoratorB : public Decorator {
public:
    ConcreteDecoratorB(Component* component) : Decorator(component) {}

    std::string operation() override {
        return "ConcreteDecoratorB(" + Decorator::operation() + ")";
    }
};

int main() {
    Component* component = new ConcreteComponent();
    Component* decoratorA = new ConcreteDecoratorA(component);
    Component* decoratorB = new ConcreteDecoratorB(decoratorA);

    std::cout << decoratorB->operation() << std::endl; // 输出: ConcreteDecoratorB(ConcreteDecoratorA(ConcreteComponent))

    delete decoratorB; // 注意：这里会自动删除 decoratorA 和 component，因为 Decorator 的析构函数会删除其持有的 component 指针
    //不需要手动 delete decoratorA 和 component，否则会导致 double free

    return 0;
}