C++观察者模式实现事件通知机制

#include <iostream>
#include <vector>
#include <algorithm>
// 观察者接口
class Observer {
public:
virtual ~Observer() = default;
virtual void update(const std::string& message) = 0;
};
// 被观察者
class Subject {
private:
std::vector<Observer*> observers;
std::string state;
public:
void attach(Observer* obs) {
observers.push_back(obs);
}
void detach(Observer* obs) {
    observers.erase(
        std::remove(observers.begin(), observers.end(), obs),
        observers.end()
    );
}

void notify() {
    for (auto* obs : observers) {
        obs-&gt;update(state);
    }
}

void setState(const std::string&amp; new_state) {
    state = new_state;
    notify();
}

std::string getState() const {
    return state;
}
};
// 具体观察者
class ConcreteObserver : public Observer {
private:
std::string name;
public:
ConcreteObserver(const std::string& n) : name(n) {}
void update(const std::string&amp; message) override {
    std::cout &lt;&lt; name &lt;&lt; " 收到通知: " &lt;&lt; message &lt;&lt; "\n";
}
};

int main() {
    Subject subject;
    ConcreteObserver observer1("ObserverA");
    ConcreteObserver observer2("ObserverB");
subject.attach(&observer1);
subject.attach(&observer2);

subject.setState("事件触发：系统更新");
// 输出：
// ObserverA 收到通知: 事件触发：系统更新
// ObserverB 收到通知: 事件触发：系统更新

subject.detach(&observer2);
subject.setState("事件触发：用户登录");
// 仅 ObserverA 收到通知

return 0;
}