C++中的装饰器模式

本文主要是介绍C++中的装饰器模式，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

装饰器模式（Decorator Pattern）

实际应用

图形对象装饰器

数据流装饰器

网络请求装饰器

总结

装饰器模式（Decorator Pattern）

装饰器模式是一种结构型设计模式，它允许你动态地向一个对象添加新的行为，而不改变其接口。这种模式通过将对象放入包含行为的特殊封装对象（装饰器）中来实现。装饰器模式提供了一种灵活的替代继承的方式来扩展对象的功能。

实际应用

图形对象装饰器

假设有一个图形对象，可能需要动态地添加边框、颜色等装饰。

#include <iostream>
#include <memory>// 图形接口
class Shape {
public:virtual ~Shape() = default;virtual void draw() const = 0;
};// 具体实现：圆形
class Circle : public Shape {
public:void draw() const override {std::cout << "Drawing Circle\n";}
};// 具体实现：矩形
class Rectangle : public Shape {
public:void draw() const override {std::cout << "Drawing Rectangle\n";}
};// 装饰器基类
class ShapeDecorator : public Shape {
protected:std::shared_ptr<Shape> decoratedShape;
public:ShapeDecorator(std::shared_ptr<Shape> shape) : decoratedShape(shape) {}virtual void draw() const override {decoratedShape->draw();}
};// 具体装饰器：添加红色边框
class RedBorderDecorator : public ShapeDecorator {
public:RedBorderDecorator(std::shared_ptr<Shape> shape) : ShapeDecorator(shape) {}void draw() const override {decoratedShape->draw();setRedBorder();}void setRedBorder() const {std::cout << "Adding Red Border\n";}
};// 具体装饰器：添加蓝色背景
class BlueBackgroundDecorator : public ShapeDecorator {
public:BlueBackgroundDecorator(std::shared_ptr<Shape> shape) : ShapeDecorator(shape) {}void draw() const override {decoratedShape->draw();setBlueBackground();}void setBlueBackground() const {std::cout << "Adding Blue Background\n";}
};int main() {std::shared_ptr<Shape> circle = std::make_shared<Circle>();std::shared_ptr<Shape> redCircle = std::make_shared<RedBorderDecorator>(circle);std::shared_ptr<Shape> blueRedCircle = std::make_shared<BlueBackgroundDecorator>(redCircle);std::cout << "Circle with normal border:\n";circle->draw();std::cout << "\nCircle with red border:\n";redCircle->draw();std::cout << "\nCircle with red border and blue background:\n";blueRedCircle->draw();return 0;
}

数据流装饰器

假设有一个数据流，可以动态地向数据流添加不同的处理，如加密、压缩等。

#include <iostream>
#include <memory>
#include <string>// 数据流接口
class DataStream {
public:virtual ~DataStream() = default;virtual void write(const std::string& data) = 0;
};// 具体实现：文件数据流
class FileDataStream : public DataStream {
public:void write(const std::string& data) override {std::cout << "Writing data to file: " << data << "\n";}
};// 装饰器基类
class DataStreamDecorator : public DataStream {
protected:std::shared_ptr<DataStream> wrappee;
public:DataStreamDecorator(std::shared_ptr<DataStream> stream) : wrappee(stream) {}void write(const std::string& data) override {wrappee->write(data);}
};// 具体装饰器：加密数据流
class EncryptedDataStream : public DataStreamDecorator {
public:EncryptedDataStream(std::shared_ptr<DataStream> stream) : DataStreamDecorator(stream) {}void write(const std::string& data) override {std::string encryptedData = encrypt(data);DataStreamDecorator::write(encryptedData);}std::string encrypt(const std::string& data) {return "Encrypted(" + data + ")";}
};// 具体装饰器：压缩数据流
class CompressedDataStream : public DataStreamDecorator {
public:CompressedDataStream(std::shared_ptr<DataStream> stream) : DataStreamDecorator(stream) {}void write(const std::string& data) override {std::string compressedData = compress(data);DataStreamDecorator::write(compressedData);}std::string compress(const std::string& data) {return "Compressed(" + data + ")";}
};int main() {std::shared_ptr<DataStream> fileStream = std::make_shared<FileDataStream>();std::shared_ptr<DataStream> encryptedStream = std::make_shared<EncryptedDataStream>(fileStream);std::shared_ptr<DataStream> compressedEncryptedStream = std::make_shared<CompressedDataStream>(encryptedStream);std::cout << "Writing plain data to file:\n";fileStream->write("Hello World");std::cout << "\nWriting encrypted data to file:\n";encryptedStream->write("Hello World");std::cout << "\nWriting compressed and encrypted data to file:\n";compressedEncryptedStream->write("Hello World");return 0;
}

网络请求装饰器

假设有一个网络请求对象，可以动态地添加日志记录、重试等功能。

#include <iostream>
#include <memory>
#include <string>// 网络请求接口
class NetworkRequest {
public:virtual ~NetworkRequest() = default;virtual void execute() const = 0;
};// 具体实现：基础网络请求
class BasicNetworkRequest : public NetworkRequest {
public:void execute() const override {std::cout << "Executing basic network request\n";}
};// 装饰器基类
class NetworkRequestDecorator : public NetworkRequest {
protected:std::shared_ptr<NetworkRequest> wrappee;
public:NetworkRequestDecorator(std::shared_ptr<NetworkRequest> request) : wrappee(request) {}void execute() const override {wrappee->execute();}
};// 具体装饰器：日志记录
class LoggingNetworkRequest : public NetworkRequestDecorator {
public:LoggingNetworkRequest(std::shared_ptr<NetworkRequest> request) : NetworkRequestDecorator(request) {}void execute() const override {log();NetworkRequestDecorator::execute();}void log() const {std::cout << "Logging network request\n";}
};// 具体装饰器：重试机制
class RetryNetworkRequest : public NetworkRequestDecorator {
private:int retries;
public:RetryNetworkRequest(std::shared_ptr<NetworkRequest> request, int retries) : NetworkRequestDecorator(request), retries(retries) {}void execute() const override {for (int i = 0; i < retries; ++i) {try {NetworkRequestDecorator::execute();return;} catch (...) {std::cout << "Retry " << i + 1 << " failed\n";}}std::cout << "All retries failed\n";}
};int main() {std::shared_ptr<NetworkRequest> basicRequest = std::make_shared<BasicNetworkRequest>();std::shared_ptr<NetworkRequest> loggedRequest = std::make_shared<LoggingNetworkRequest>(basicRequest);std::shared_ptr<NetworkRequest> retriedLoggedRequest = std::make_shared<RetryNetworkRequest>(loggedRequest, 3);std::cout << "Executing basic request:\n";basicRequest->execute();std::cout << "\nExecuting logged request:\n";loggedRequest->execute();std::cout << "\nExecuting retried and logged request:\n";retriedLoggedRequest->execute();return 0;
}