如何在C++中实现一个观察者模式_C++观察者设计模式实现教程

#include <iostream>
#include <vector>

class Observer {
public:
    virtual void update(int state) = 0;
};

class Subject {
public:
    virtual void attach(Observer* observer) = 0;
    virtual void detach(Observer* observer) = 0;
    virtual void notify() = 0;
};

class ConcreteSubject : public Subject {
private:
    std::vector<Observer*> observers;
    int state;

public:
    void attach(Observer* observer) override {
        observers.push_back(observer);
    }

    void detach(Observer* observer) override {
        for (auto it = observers.begin(); it != observers.end(); ++it) {
            if (*it == observer) {
                observers.erase(it);
                return;
            }
        }
    }

    void notify() override {
        for (Observer* observer : observers) {
            observer->update(state);
        }
    }

    void setState(int state) {
        this->state = state;
        notify();
    }

    int getState() {
        return state;
    }
};

class ConcreteObserver : public Observer {
private:
    ConcreteSubject* subject;
    int observerState;

public:
    ConcreteObserver(ConcreteSubject* subject) : subject(subject) {}

    void update(int state) override {
        observerState = state;
        std::cout << "Observer state updated to: " << observerState << std::endl;
    }
};

int main() {
    ConcreteSubject* subject = new ConcreteSubject();

    ConcreteObserver* observer1 = new ConcreteObserver(subject);
    ConcreteObserver* observer2 = new ConcreteObserver(subject);

    subject->attach(observer1);
    subject->attach(observer2);

    subject->setState(10);
    subject->setState(20);

    subject->detach(observer1);
    subject->setState(30);

    delete observer1;
    delete observer2;
    delete subject;

    return 0;
}