只是自己的一個記錄過程，不做詳細解說

這是這次寫的一個流程

Observer.h

#ifndef _OBSERVER_H_
#define _OBSERVER_H_

#include <map>
#include <mutex>

using namespace std;

class Msg
{
public:
	virtual int GetMsgID() = 0;

	virtual void* GetMsg() = 0;

};

class MsgContainer;

class Subscriber
{
public:
	virtual void subscribe(MsgContainer *pMsgContainer, int MsgID);

	virtual void unsubscribe(MsgContainer *pMsgContainer, int MsgID);

	virtual void handleMsg(Msg *msg) = 0;
};

class MsgContainer
{
public:
	virtual void add_subscriber(Subscriber *pSubscriber, int MsgID);

	virtual void remove_subscriber(Subscriber *pSubscriber, int MsgID);

	virtual void receiveMsg(Msg *msg);

protected:
	virtual void notify(Msg *msg);

private:
	multimap<int, Subscriber*> m_subscriber;
	mutex m_mutex;
};

class Publisher
{
public:
	virtual void sendMsg(MsgContainer *pMsgContainer, Msg *msg);
};

class MsgImp :public Msg
{
public:
	MsgImp(int MsgID, void *Msgfield);

	virtual ~MsgImp();

	virtual int GetMsgID();

	virtual void* GetMsg();

private:
	int m_MsgID;

	void *m_Msgfield;
};

class SubscriberImp :public Subscriber
{
public:
	SubscriberImp();

	virtual ~SubscriberImp();

	virtual void handleMsg(Msg *msg);
private:
	void *m_expext_field;
};

class SubscriberImp2 :public Subscriber
{
public:
	SubscriberImp2();
	virtual ~SubscriberImp2();

	virtual void handleMsg(Msg *msg);
private:
	void *m_expext_field;
};

class PublisherImp :public Publisher
{
public:
	PublisherImp();

	virtual ~PublisherImp();
};

#endif
 

#include "Observer.h"
#include <iostream>

using namespace std;


MsgImp::MsgImp(int MsgID, void *Msgfield)
{
	m_MsgID = MsgID;
	m_Msgfield = Msgfield;
}

MsgImp::~MsgImp()
{

}

int MsgImp::GetMsgID()
{
	return m_MsgID;
}

void * MsgImp::GetMsg()
{
	return m_Msgfield;
}

void Subscriber::subscribe(MsgContainer *pMsgContainer, int MsgID)
{
	pMsgContainer->add_subscriber(this, MsgID);
}

void Subscriber::unsubscribe(MsgContainer *pMsgContainer, int MsgID)
{
	pMsgContainer->remove_subscriber(this, MsgID);
}

SubscriberImp::SubscriberImp()
{

};

SubscriberImp::~SubscriberImp()
{
	delete m_expext_field;
};

void SubscriberImp::handleMsg(Msg *msg)
{
	m_expext_field = msg->GetMsg();
	
	cout << "this is the SubscriberImp1..." << endl;
	cout << "the MsgID is " << msg->GetMsgID() << endl;
	cout <<(char *) msg->GetMsg() << ", SubscriberImp1 handle the msg"<<endl;
}

SubscriberImp2::SubscriberImp2()
{

};

SubscriberImp2::~SubscriberImp2()
{
	delete m_expext_field;
};

void SubscriberImp2::handleMsg(Msg *msg)
{
	m_expext_field = msg->GetMsg();
	
	cout << "this is the SubscriberImp2..." << endl;
	cout << "the MsgID is " << msg->GetMsgID() << endl;
	cout << (char *)msg->GetMsg() << ", SubscriberImp2 handle the msg"<< endl;
}

void MsgContainer::add_subscriber(Subscriber *pSubscriber, int MsgID)
{
	lock_guard<mutex> guard(m_mutex);

	if (m_subscriber.empty())
	{
		m_subscriber.insert(make_pair(MsgID, pSubscriber));
	}

	bool isExist = false;
	map<int, Subscriber*>::iterator it = m_subscriber.lower_bound(MsgID);
	while (it != m_subscriber.upper_bound(MsgID))
	{
		if (it->second == pSubscriber)
			isExist = true;
		it++;
	}
	if (!isExist)
	{
		m_subscriber.insert(make_pair(MsgID, pSubscriber));
	}
}

void MsgContainer::remove_subscriber(Subscriber *pSubscriber, int MsgID)
{
	lock_guard<mutex> guard(m_mutex);

	if (m_subscriber.empty())
	{
		return;
	}

	multimap<int, Subscriber*>::iterator it = m_subscriber.lower_bound(MsgID);
	while (it != m_subscriber.upper_bound(MsgID))
	{
		if (it->second == pSubscriber)
		{
			m_subscriber.erase(it);
			break;
		}
		it++;
	}
}

void MsgContainer::notify(Msg *msg)
{
	multimap<int, Subscriber*>::iterator it = m_subscriber.lower_bound(msg->GetMsgID());
	for (; it != m_subscriber.upper_bound(msg->GetMsgID()); it++)
	{
		it->second->handleMsg(msg);
	}
}

void MsgContainer::receiveMsg(Msg *msg)
{
	lock_guard<mutex> guard(m_mutex);

	this->notify(msg);
}


void Publisher::sendMsg(MsgContainer *pMsgContainer, Msg *msg)
{
	pMsgContainer->receiveMsg(msg);
}

PublisherImp::PublisherImp(){};
PublisherImp::~PublisherImp(){};
 

#include "Observer.h"
#include <iostream>

using namespace std;

int main()
{
	Subscriber *subscriber = NULL;
	MsgContainer *msgcontainer = new MsgContainer();
	Msg *msg = NULL;
	Publisher *publisher = NULL;

	char *msgfield = NULL;

	subscriber = new SubscriberImp();
	subscriber->subscribe(msgcontainer, 2);

	Subscriber *subscriber2 = NULL;
	subscriber2 = new SubscriberImp2();
	subscriber2->subscribe(msgcontainer, 2);

	msgfield = "the publisher send this msg";
	msg = new MsgImp(2,msgfield);

	publisher = new PublisherImp();
	publisher->sendMsg(msgcontainer,msg);

	subscriber2->unsubscribe(msgcontainer,2);

	msgfield = "the publisher send this msg2";
	msg = new MsgImp(2, msgfield);
	publisher = new PublisherImp();
	publisher->sendMsg(msgcontainer, msg);

	return 0;
}