c++设计模式（观察者模式）

来源：互联网发布：社交软件后台架构编辑：程序博客网时间：2024/06/14 16:52

GOOD：定义了一种一对多的关系，让多个观察对象（公司员工）同时监听一个主题对象（秘书），主题对象状态发生变化时，会通知所有的观察者，使它们能够更新自己。
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 例：#include <string>#include <iostream>#include <vector>using namespace std;class Secretary;//看股票的同事类（观察对象，观察者）class StockObserver{private:    string name;    Secretary* sub;public:    StockObserver(string strname,Secretary* strsub)    {        name=strname;        sub=strsub;    }    void Update();};//秘书类（主题对象，通知者）class Secretary{private:    vector<StockObserver> observers;public:    string action;    void Add(StockObserver ob)    {        observers.push_back(ob);    }    void Notify()    {        vector<StockObserver>::iterator p = observers.begin();        while (p!=observers.end())        {            (*p).Update();            p++;        }    }};void StockObserver::Update(){    cout<<name<<":"<<sub->action<<",不要玩股票了，要开始工作了"<<endl;}//客户端int main(){    Secretary *p=new Secretary();  //创建通知者    //观察者    StockObserver *s1= new StockObserver("小李",p);    StockObserver *s2 = new StockObserver("小赵",p);    //加入通知队列    p->Add(*s1);    p->Add(*s2);    //事件    p->action="老板来了";    //通知    p->Notify();    return 0;}

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例：#include <string>#include <iostream>#include <vector>using namespace std;class SecretaryBase;//抽象观察者class CObserverBase{protected:    string name;    SecretaryBase* sub;public:    CObserverBase(string strname,SecretaryBase* strsub)    {        name=strname;        sub=strsub;    }    virtual void Update()=0;};//具体的观察者，看股票的class StockObserver : public CObserverBase{public:    StockObserver(string strname,SecretaryBase* strsub) : CObserverBase(strname,strsub)    {    }    virtual void Update();};//具体观察者，看NBA的class NBAObserver : public CObserverBase{public:    NBAObserver(string strname,SecretaryBase* strsub) : CObserverBase(strname,strsub){}    virtual void Update();};//抽象通知者class SecretaryBase{public:    string action;    vector<CObserverBase*> observers;public:    virtual void Attach(CObserverBase* observer)=0;    virtual void Notify()=0;};//具体通知者class Secretary :public SecretaryBase{public:    void Attach(CObserverBase* ob)    {        observers.push_back(ob);    }    void Notify()    {        vector<CObserverBase*>::iterator p = observers.begin();        while (p!=observers.end())        {            (*p)->Update();            p++;        }    }};void StockObserver::Update(){    cout<<name<<":"<<sub->action<<",不要玩股票了，要开始工作了"<<endl;}void NBAObserver::Update(){    cout<<name<<":"<<sub->action<<",不要看NBA了，老板来了"<<endl;}客户端：int main(){    SecretaryBase *p=new Secretary();  //创建观察者    //被观察的对象    CObserverBase *s1= new NBAObserver("小李",p);    CObserverBase *s2 = new StockObserver("小赵",p);    //加入观察队列    p->Attach(s1);    p->Attach(s2);    //事件    p->action="老板来了";    //通知    p->Notify();    return 0;}

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