观察者模式

一、发布者

添加订阅者

移除订阅者

将消息通知给订阅者列表

#pragma once
#include <iostream>
#include <string>
#include <list>
#include "Observer.h"


class SendSignaler
{
public:
    virtual void attach(Observer* handle) = 0;
    virtual void detach(Observer* handle) = 0;
    virtual void notify(std::string strMsg) = 0;

protected:
    std::list<Observer*> mObserverList;
};


class SendSignaler1 : public virtual SendSignaler
{
public:
    void attach(Observer* handle) override
    {
        mObserverList.emplace_back(handle);
    }

    void detach(Observer* handle) override
    {
        mObserverList.remove(handle);
    }

    void notify(std::string strMsg) override
    {
        std::cout << "当前观察者有:" << mObserverList.size() << "人。" << std::endl;
        for (const auto& it : mObserverList)
        {
            it->update(strMsg);
        }
    }
};

二、订阅者

接受消息通知进行相应响应

#pragma once
#include <iostream>
#include <string>
#include "Signal.h"

class Observer
{
public:
    virtual void update(std::string& strReceiveMsg) = 0;
};


class Observer1 : public Observer
{
public:
    void update(std::string& strReceiveMsg) override
    {
        std::cout << "观察者1收到:" << strReceiveMsg << std::endl;
    }
};

class Observer2 : public Observer
{
public:
    void update(std::string& strReceiveMsg) override
    {
        std::cout << "观察者2收到:" << strReceiveMsg << std::endl;
    }
};

==============================================================

测试：

#include "Signal.h"
#include "Observer.h"

int main()
{
    SendSignaler1 Sender1;
    Observer1 Receiver1;
    Observer2 Receiver2;
    Sender1.attach(&Receiver1);
    Sender1.attach(&Receiver2);
    Sender1.notify("下达任务XXX");
    Sender1.detach(&Receiver1);
    Sender1.notify("...................");
    system("pause");
    return 0;
}