Observer （C++实现）

// Observer.cpp : 定义控制台应用程序的入口点。//

#include "stdafx.h"#include <iostream>#include <list>#include <algorithm>

 

using namespace std;

 

typedef int STATE;

 

class Observer;

class Subject{public: Subject() : m_nSubjectState(-1){} virtual ~Subject();

 void Notify();        void Attach(Observer *pObserver);   void Detach(Observer *pObserver);  

 virtual void SetState(STATE nState);   virtual STATE  GetState();  

protected: STATE  m_nSubjectState;      list<Observer*> m_ListObserver; };

class Observer{public: Observer() : m_nObserverState(-1){} virtual ~Observer(){}

 virtual void Update(Subject* pSubject) = 0;

protected: STATE m_nObserverState;     };

class ConcreateSubject : public Subject{public: ConcreateSubject() : Subject(){} virtual ~ConcreateSubject() {    }

 virtual void SetState(STATE nState);   virtual STATE  GetState(); 

};

class ConcreateObserver : public Observer{public: ConcreateObserver() : Observer(){} virtual ~ConcreateObserver(){}

 virtual void Update(Subject* pSubject);};

void Subject::Attach(Observer *pObserver){  cout<<"Attach an Observer"<<endl;  m_ListObserver.push_back(pObserver);}

void Subject::Detach(Observer *pObserver){ std::list<Observer*>::iterator iter; iter =find(m_ListObserver.begin(), m_ListObserver.end(), pObserver); if (m_ListObserver.end() != iter) {  m_ListObserver.erase(iter);  cout << "Detach an Observer"<<endl; } else {  cout<<"No this Observer,so cannot detach it"<<endl; }}

void Subject::Notify(){ cout<<"Notify  to all observers"<<endl; list<Observer*>::iterator iter; for (iter= m_ListObserver.begin();iter!= m_ListObserver.end();iter++) {  (*iter)->Update(this); }}

void Subject::SetState(STATE nState){ m_nSubjectState = nState;}

STATE Subject::GetState(){ return m_nSubjectState;}

Subject::~Subject(){

 std::list<Observer*>::iterator iter, temp;

 for (iter= m_ListObserver.begin(); iter!= m_ListObserver.end();) {  temp = iter;  ++iter;   delete (*temp); }  m_ListObserver.clear();}

void ConcreateSubject::SetState(STATE nState){ std::cout << "SetState By ConcreateSubject/n"; m_nSubjectState = nState;}

STATE ConcreateSubject::GetState(){ std::cout << "GetState By ConcreateSubject/n"; return m_nSubjectState;}void ConcreateObserver::Update(Subject* pSubject){ if (NULL == pSubject)  return;

 m_nObserverState = pSubject->GetState();

 std::cout << "The ObeserverState is " << m_nObserverState << std::endl;}

int _tmain(int argc, _TCHAR* argv[]){ Observer *p1 = new ConcreateObserver(); Observer *p2 = new ConcreateObserver();

 Subject* p = new ConcreateSubject(); p->Attach(p1); p->Attach(p2); p->SetState(8); p->Notify();

 p->Detach(p1); p->SetState(10); p->Notify();

 delete p; return 0;}