C++ 设计模式-观察者模式

股票监控系统（多用户、多股票）

系统需求

1. 支持同时监控多个股票代码（如 AAPL、GOOGL、TSLA）
2. 每个用户可以订阅不同股票的价格变动
3. 支持不同策略组合（价格警报、自动交易、日志记录）
4. 实时显示不同用户的订阅状态

完整实现代码

#include <iostream>
#include <string>
#include <vector>
#include <unordered_map>
#include <memory>
#include <thread>
#include <mutex>
#include <atomic>
#include <random>
#include <iomanip>
#include <chrono>
#include <algorithm>
#include <initializer_list>

// 前向声明
class StockEvent;
class PriceUpdateEvent;

// 类型别名
using StockSymbol = std::string;
using UserID = std::string;

// 抽象观察者接口
class TradingStrategy {
   
public:
    virtual ~TradingStrategy() = default;
    virtual void handleEvent(const StockEvent& event) = 0;
    virtual std::vector<StockSymbol> subscribedSymbols() const = 0;
};

// 事件基类
class StockEvent {
   
public:
    virtual ~StockEvent() = default;
    virtual StockSymbol symbol() const = 0;
    virtual double price() const = 0;
    virtual std::string toString() const = 0;
};

// 具体股票事件
class PriceUpdateEvent : public StockEvent {
   
    StockSymbol _symbol;
    double _price;
    std::chrono::system_clock::time_point _timestamp;

public:
    PriceUpdateEvent(StockSymbol sym, double price)
        : _symbol(std::move(sym)), _price(price),
          _timestamp(std::chrono::system_clock::now()) {
   }

    StockSymbol symbol() const override {
    return _symbol; }
    double price() const override {
    return _price; }

    std::string toString() const override {
   
        std::time_t t = std::chrono::system_clock::to_time_t(_timestamp);
        std::stringstream ss;
        ss << _symbol << " $" << std::fixed << std::setprecision(2) << _price
           << " @ " << std::ctime(&t);
        return ss.str();
    }
};

// 股票交易所核心
class StockExchange {
   
    struct StockData {
   
        double basePrice;
        std::atomic<double> currentPrice;
        std::vector<std::shared_ptr<TradingStrategy>> subscribers;
        StockData(const StockData&) = delete;
        // 添加构造函数
        StockData(double base, double current, std::vector<std::shared_ptr<TradingStrategy>>&& subs)
            : basePrice(base),
              currentPrice(current),
              subscribers(std::move(subs)) {
   }
    };

    std::unordered_map<StockSymbol, StockData*> _stocks;
    mutable std::mutex _mutex;
    std::atomic<bool> _running{
   true};
    std::vector<std::thread> _workers;

    // 价格生成器
    double generateNewPrice(double base) {
   
        static std::mt19937 gen(std::random_device{
   }());
        std::normal_distribution<> dist(0, base * 0.02);
        return base + dist(gen);
    }

    /