16.1.解释
概念：定义对象间的一种一对多的依赖关系，当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并被自动更新。
main()，
IObservable，被观察者接口
CHanFeiZiObservable，被观察者韩非子
IObserver，观察者接口
CLiSiObserver，观察者李斯
CZhouSiObserver观察者周斯
说明：将观察者聚集到被观察者韩非子身边，韩非子的每一个举动都会通知给观察者，如李斯或周斯。
注意：最多允许一个对象既是观察者也是被观察者。就像数据库中的触发器一样，成为一个复杂的链就很难维护了。观察者类似于委托的处理方式。
//IObservable.h
#pragma once
#include "IObserver.h"
#include <iostream>
using std::string;
class IObservable
{
public:
IObservable(void)
{
}
virtual ~IObservable(void)
{
}
virtual void AddObserver(IObserver *pObserver) = 0;
virtual void DeleteObserver(IObserver *pObserver) = 0;
virtual void NotifyObservers(string context) = 0;
};
//HanFeiziObservable.h
#pragma once
#include "iobservable.h"
#include "IObserver.h"
#include <vector>
using std::vector;
class CHanFeiziObservable :
public IObservable
{
public:
CHanFeiziObservable(void);
~CHanFeiziObservable(void);
void AddObserver(IObserver *pObserver);
void DeleteObserver(IObserver *pObserver);
void NotifyObservers(string context);
void HaveBreakfast();
void HaveFun();
private:
vector<IObserver*> m_observerList;
typedef vector<IObserver*>::const_iterator ObserverList_C_iterator;
};
//HanFeiziObservable.cpp
#include "StdAfx.h"
#include "HanFeiziObservable.h"
#include <iostream>
using std::string;
using std::cout;
using std::endl;
CHanFeiziObservable::CHanFeiziObservable(void)
{
}
CHanFeiziObservable::~CHanFeiziObservable(void)
{
}
void CHanFeiziObservable::AddObserver( IObserver *pObserver )
{
m_observerList.push_back(pObserver);
}
void CHanFeiziObservable::DeleteObserver( IObserver *pObserver )
{
ObserverList_C_iterator it = m_observerList.begin();
for (; it != m_observerList.end(); it++)
{
string name = (*it)->GetName();
if (name.compare(pObserver->GetName()) == 0)
{
//找到了删除。
}
}
}
void CHanFeiziObservable::NotifyObservers( string context )
{
ObserverList_C_iterator it = m_observerList.begin();
for (; it != m_observerList.end(); it ++)
{
(*it)->Update(context);
}
}
void CHanFeiziObservable::HaveBreakfast()
{
cout << "韩非子：开始吃饭了..." << endl;
this->NotifyObservers("韩非子在吃饭");
}
void CHanFeiziObservable::HaveFun()
{
cout << "韩非子：开始娱乐了..." << endl;
this->NotifyObservers("韩非子在娱乐");
}
//IObserver.h
#pragma once
#include <iostream>
using std::string;
class IObserver
{
public:
IObserver(string _name)
{
this->m_name = _name;
}
virtual ~IObserver(void)
{
}
virtual void Update(string context) = 0;
virtual string GetName() = 0;//为c++单独增加的函数，用于删除时查找观察者。
protected:
string m_name;
};
//LiSiObserver.h
#pragma once
#include "iobserver.h"
#include <iostream>
using std::string;
class CLiSiObserver :
public IObserver
{
public:
CLiSiObserver(void);
~CLiSiObserver(void);
void Update(string context);
string GetName();
private:
void ReportToQinShiHuang(string report);
};
//LiSiObserver.cpp
#include "StdAfx.h"
#include "LiSiObserver.h"
#include <iostream>
using std::cout;
using std::endl;
using std::string;
CLiSiObserver::CLiSiObserver(void) : IObserver("李斯")
{
}
CLiSiObserver::~CLiSiObserver(void)
{
}
void CLiSiObserver::Update( string context )
{
cout << "李斯：观察到韩非子活动，开始向老板汇报了..." << endl;
this->ReportToQinShiHuang(context);
cout << "李斯：汇报完毕，秦老板赏给他两个萝卜吃吃..." << endl;
}
void CLiSiObserver::ReportToQinShiHuang( string report )
{
cout << "李斯：报告，秦老板！韩非子有活动了--->" << report.c_str() << endl;
}
string CLiSiObserver::GetName()
{
return m_name;
}
//ZhouSiObserver.h
#pragma once
#include "iobserver.h"
#include <iostream>
using std::string;
class CZhouSiObserver :
public IObserver
{
public:
CZhouSiObserver(void);
~CZhouSiObserver(void);
void Update(string context);
string GetName();
private:
void Cry(string report);
};
//ZhouSiObserver.cpp
#include "StdAfx.h"
#include "ZhouSiObserver.h"
#include <iostream>
using std::cout;
using std::endl;
using std::string;
CZhouSiObserver::CZhouSiObserver(void) : IObserver("周斯")
{
}
CZhouSiObserver::~CZhouSiObserver(void)
{
}
void CZhouSiObserver::Update( string context )
{
cout << "周斯：观察到韩非子活动，自己也开始活动了..." << endl;
this->Cry(context);
cout << "周斯：真真的哭列了..." << endl;
}
void CZhouSiObserver::Cry( string report )
{
cout << "周斯：为因" << report.c_str() << ", ————所以我悲伤呀！" << endl;
}
string CZhouSiObserver::GetName()
{
return m_name;
}
// Observer.cpp
#include "stdafx.h"
#include "HanFeiZi.h"
#include "LiSi.h"
#include "HanFeiZiNew.h"
#include "HanFeiziObservable.h"
#include "LiSiObserver.h"
#include "ZhouSiObserver.h"
#include <iostream>
using std::cout;
using std::endl;
using std::string;
void DoNew()
{
//IHanFeiZi.h, HanFeiZiNew.h, ILiSi.h, LiSi.h
// cout << "----------用新的方法试试----------" << endl;
//CHanFeiZiNew hanfeizi;
//hanfeizi.HaveBreakfast();
//hanfeizi.HaveFun();
}
void DoNewNew()
{
//IObservable.h, HanfeiziObservable.h, IObserver.h, LiSiObserver.h
cout << "----------用更新的方法再试试----------" << endl;
IObserver *pLiSi = new CLiSiObserver();
IObserver *pZhouSi = new CZhouSiObserver();
CHanFeiziObservable *pHanFeiZi = new CHanFeiziObservable();
pHanFeiZi->AddObserver(pLiSi);
pHanFeiZi->AddObserver(pZhouSi);
pHanFeiZi->HaveBreakfast();
delete pLiSi;
pLiSi = NULL;
delete pHanFeiZi;
pHanFeiZi = NULL;
}
int _tmain(int argc, _TCHAR* argv[])
{
//比较原始的方法，用线程来观察。
//DoIt();
//把李斯这个类聚集到韩非子这个类上，这样的话耦合度太高了，还是用更抽象的方式。
DoNew();
//更抽象的方式，想要观察韩非子的人多了去了，不可能只允许李斯观察。
DoNewNew();
_CrtSetDbgFlag(_CRTDBG_LEAK_CHECK_DF | _CRTDBG_ALLOC_MEM_DF);
_CrtDumpMemoryLeaks();
return 0;
}
观察者模式属于行为型模式。
