设计模式：观察者模式

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

开始订订阅，和调用了

　　


 

 

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;

}