观察者模式

来源：互联网发布：外国人可以开淘宝店吗编辑：程序博客网时间：2024/05/13 14:19

今天介绍另一种模式

观察者模式是我们经常用的一个模式，比如在用wcf做服务的时候通知客户端做一些操作一般用设计者模式。

今天做一个订报纸的小例子来理解一下观察者模式出版者+订阅者=观察者模式

用下边的图来说就是人民日报+订阅者=观察者模式

只要是订阅了人民日报的人，有了新报纸就会送到订阅者那里去，

当你不想订的时候取消就不订阅就不会再收到报纸了。

下面我们就来用代码实现一下这个模式

//报纸接口
   public interface INewsPaper
   {
       //添加订阅者
       void RegisterSubscriber(ISubScribe f_subScribe);
       //取消订阅
       void RemoveSubScriber(ISubScribe f_subScribe);
       //发送报纸
       void SendPaper();
   }
 
   //订阅者
   public interface ISubScribe
   {
       //有新的报纸了就会被执行通知
       void HasNewPaper();
   }
 
   //人民日报
   public class PeopleNewsPaper : INewsPaper
   {
       private List<ISubScribe> subList = new List<ISubScribe>();
       public void RegisterSubscriber(ISubScribe f_subScribe)
       {
           subList.Add(f_subScribe);
       }
 
       public void RemoveSubScriber(ISubScribe f_subScribe)
       {
           if (subList.IndexOf(f_subScribe) >= 0)
           {
               subList.Remove(f_subScribe);
           }
       }
 
       //发报纸啦~~
       public void SendPaper()
       {
           foreach (ISubScribe _sub in subList)
           {
               _sub.HasNewPaper();
           }
       }     
   }
 
   public class subHuman : ISubScribe
   {
       //订阅者的名字
       private string p_name;
 
       public subHuman(string f_name)
       {
           p_name = f_name;
       }
       //告诉订阅者有新报纸了
       public void HasNewPaper()
       {
           Console.WriteLine(p_name + "!! 有新的报纸了，请查收！");
       }
        
   }

开始订订阅，和调用了

static void Main(string[] args)
        {
            PeopleNewsPaper _paper = new PeopleNewsPaper();
            subHuman _XiaoMing = new subHuman("小明");
            subHuman _ZhaoYun = new subHuman("赵云");
            subHuman _LiuBei = new subHuman("刘备");
            //小明订报
            _paper.RegisterSubscriber(_XiaoMing);
            //赵云订报
            _paper.RegisterSubscriber(_ZhaoYun);
            //刘备订报
            _paper.RegisterSubscriber(_LiuBei);
            //有新报纸了
            _paper.SendPaper();
            Console.WriteLine("---------------发完报纸了------------------");
 
            //小明不想订了，取消报纸
            _paper.RemoveSubScriber(_XiaoMing);
            //又有新报纸了  就没有小明的报纸 了
            _paper.SendPaper();
            Console.ReadLine();
        }

C++代码

#pragma once#include <iostream>//订阅者class ISubScribe{public:    //有新的报纸了就会被执行通知    virtual void HasNewPaper() = 0;    virtual ~ISubScribe(){}};//报纸接口class INewsPaper{public:    //添加订阅者    virtual void RegisterSubscriber(ISubScribe* f_subScribe) = 0;    //取消订阅    virtual void RemoveSubScriber(ISubScribe* f_subScribe) = 0;    //发送报纸    virtual void SendPaper() = 0;    virtual ~INewsPaper(){}};

#pragma once#include "inewspaper.h"#include <iostream>#include <vector>using namespace std;class PeopleNewsPaper :    public INewsPaper{public:    PeopleNewsPaper();    virtual ~PeopleNewsPaper();    //添加订阅者    void RegisterSubscriber(ISubScribe* f_subScribe);    //取消订阅     void RemoveSubScriber(ISubScribe* f_subScribe);    //发送报纸    void SendPaper();private:    vector<ISubScribe*> subs;};#include "PeopleNewsPaper.h"#include <algorithm>void MyClearSub(ISubScribe* sub){    if (sub) {        delete sub;        sub = nullptr;    }}PeopleNewsPaper::PeopleNewsPaper(){}PeopleNewsPaper::~PeopleNewsPaper(){    if (!subs.empty()) {        for_each(subs.begin(), subs.end(), MyClearSub);        subs.clear();    }}//添加订阅者void PeopleNewsPaper::RegisterSubscriber(ISubScribe* f_subScribe){    if (subs.empty()) {        subs.push_back(f_subScribe);    }    else if (find(subs.begin(), subs.end(), f_subScribe) == subs.end()) {        subs.push_back(f_subScribe);    }}//取消订阅void PeopleNewsPaper::RemoveSubScriber(ISubScribe* f_subScribe){    vector<ISubScribe*>::iterator itor = find(subs.begin(), subs.end(), f_subScribe);    if (itor != subs.end()) {        subs.erase(itor);        MyClearSub(f_subScribe);    }}//发送报纸void PeopleNewsPaper::SendPaper(){    for (ISubScribe* sub : subs) {        sub->HasNewPaper();    }}

#pragma once#include "inewspaper.h"#include <iostream>#include <string>class SubHuman :    public ISubScribe{public:    SubHuman(std::string name);    ~SubHuman();    void HasNewPaper();private:    std::string m_name;};#include "SubHuman.h"using namespace std;SubHuman::SubHuman(string name){    m_name = name;}SubHuman::~SubHuman(){}void SubHuman::HasNewPaper(){    std::cout << m_name << "有报纸来了！！" << endl;}

调用

#include <iostream>#include "inewspaper.h"#include "PeopleNewsPaper.h"#include "SubHuman.h"int main(){    INewsPaper* peopPaper = new PeopleNewsPaper();    ISubScribe* sub = new SubHuman("小李");    peopPaper->RegisterSubscriber(sub);    sub = new SubHuman("小张");    peopPaper->RegisterSubscriber(sub);    sub = new SubHuman("小刘");    peopPaper->RegisterSubscriber(sub);    peopPaper->SendPaper();    peopPaper->RemoveSubScriber(sub);    peopPaper->SendPaper();    delete peopPaper;}

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