[C++知识库]C++ —— 观察者模式简记

//Observer.h

#pragma once

#include <stdio.h>
#include <mutex>
#include <list>
#include <iostream>

using namespace std;

class CObserver
{
public:
	CObserver(int nType);
	virtual ~CObserver() {};
	virtual void OnNotify(int nEvent, const char* pMsg, int nLen) {};
	virtual void SetType(int nType);
	virtual int GetType() const;

private:
	int m_nType;
};


CObserver::CObserver(int nType) :m_nType(nType)
{
	//TODU
}


void CObserver::SetType(int nType)
{
	m_nType = nType;
}


int CObserver::GetType() const
{
	return m_nType;
}



class CSubject
{
public:
	CSubject();
	virtual ~CSubject();
	virtual void Add(CObserver* po);
	virtual void Del(CObserver* po);
	virtual void Notify(CObserver* pSender, int nEvent, const char* pMsg, int dwLen);
	void ClearObserver();
	std::list<CObserver*>* GetObservers();
	CObserver* GetObserver(int nType);

private:
	list<CObserver*>* m_pListObserver;
	mutex* m_pListLock;
};


CSubject::CSubject() :m_pListObserver(NULL), m_pListLock(NULL)
{
	m_pListObserver = new list<CObserver*>;
	m_pListLock = new mutex;
}


CSubject::~CSubject()
{
	if(m_pListObserver)
	{
		m_pListObserver->clear();
		delete m_pListObserver;
		m_pListObserver = NULL;
	}

	if (m_pListLock)
	{
		delete m_pListLock;
		m_pListLock = NULL;
	}
}


void CSubject::Add(CObserver* po)
{
	if (NULL == po)
	{
		return;
	}

	m_pListLock->lock();
	
	if (find(m_pListObserver->begin(), m_pListObserver->end(), po) == m_pListObserver->end())
	{
		m_pListObserver->push_back(po);
	}
	m_pListLock->unlock();
}

void CSubject::Del(CObserver* po)
{
	if (NULL == po)
	{
		return;
	}

	m_pListLock->lock();
	if (find(m_pListObserver->begin(), m_pListObserver->end(), po) != m_pListObserver->end())
	{
		m_pListObserver->remove(po);
	}
	m_pListLock->unlock();
}

void CSubject::Notify(CObserver* pSender, int nEvevt, const char* pMsg, int dwLen)
{
	if (NULL == pSender)
	{
		return;
	}

	m_pListLock->lock();
	list<CObserver*>::iterator ite;
	ite = m_pListObserver->begin();
	while (ite != m_pListObserver->end())
	{
		CObserver* po = *(ite);
		
		//if (po == pSender) && (po != NULL) //点对点通知 通知pSender
		if ((pSender == NULL || po == pSender) && (po != NULL)) 	//广播
		{
			po->OnNotify(nEvevt, pMsg, dwLen);
		}
		ite++;
	}
	m_pListLock->unlock();
}

void CSubject::ClearObserver()
{
	m_pListLock->lock();
	m_pListObserver->clear();
	m_pListLock->unlock();
}


list<CObserver*>* CSubject::GetObservers()
{
	return m_pListObserver;
}


CObserver* CSubject::GetObserver(int nType)
{
	m_pListLock->lock();
	list<CObserver*>::iterator ite;
	ite = m_pListObserver->begin();
	while (ite != m_pListObserver->end())
	{
		CObserver* po = *(ite);
		if (po != NULL && po->GetType() == nType)
		{
			return po;
		}
		ite++;
	}
	m_pListLock->unlock();
	return NULL;
}


//派生类
class CMyObserver : public CObserver
{
public:
	CMyObserver(int nType);

	void OnNotify(int nEvent, const char* pMsg, int nLen);
};

CMyObserver::CMyObserver(int nType) : CObserver(nType) {}

void CMyObserver::OnNotify(int nEvent, const char* pMsg, int nLen)
{
	cout << nEvent << endl;
	cout << pMsg << endl;
	cout << nLen << endl;
}

//测试例

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

int main()
{

	/****************** 观察者模式验证 **********************/
	CObserver* po1 = new CMyObserver(1);
	CObserver* po2 = new CMyObserver(2);
	CSubject* psub = new CSubject();
	psub->Add(po1);
	psub->Add(po2);
	psub->Notify(po1,2021,"hello world",12);
	psub->Notify(po2, 2022, "hello world", 12);
}

//测试结果截图? 消息通知成功

?

?注：观察者模式 vs 发布订阅模式 介绍可参考下述链接

参考：https://zhuanlan.zhihu.com/p/51357583