(ZZ) 设计模式：观察者模式

 原文地址： http://www.cnblogs.com/li-peng/archive/2013/02/04/2892116.html

因为要用到观察者模式编程，翻看了一些blog。这边文章还是写得比较通俗易懂、方便理解的。

感谢原文作者！

 

 设计模式系列目录

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

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//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

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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(){}
};

View Code

#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();
    }
}

View Code

#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;
}

View Code

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;

}