设计模式学习——观察者模式（Observer Pattern）

有个报社，在有新报纸的时候，会给所有的订阅者发送推送。

 ///
 /// @file    Observer.h
 /// @author  marrs(chenchengxi993@gmail.com)
 /// @date    2017-08-20 19:54:38
 ///

#ifndef __OBSERVER_H__
#define __OBSERVER_H__

#include <iostream>
 
namespace marrs{
 
using std::cout;
using std::endl;
using std::string;

class Observer
{
    public:
        virtual ~Observer(){}
    public:
        virtual void Update(string & str_message) = 0;
    public:
        virtual string GetName() = 0;
        virtual string GetMsg() = 0;
    protected:
        string _str_name;
        string _str_message;
};

}

#endif // __OBSERVER_H__

 ///
 /// @file    Observerable.h
 /// @author  marrs(chenchengxi993@gmail.com)
 /// @date    2017-08-20 19:48:42
 ///

#ifndef __OBSERVERABLE_H__
#define __OBSERVERABLE_H__

#include <iostream>
#include <vector>

namespace marrs{
 
using std::cout;
using std::endl;
using std::string; 
using std::vector;

class Observer;
typedef vector<Observer *> ObserverCache;

class Observerable
{
    public:
        virtual ~Observerable(){}

    public:
        virtual void AddObserver(Observer * observer) = 0;
        virtual void DelObserver(Observer * observer) = 0;
        virtual void NotifyObserver(string str_message) = 0;
    protected:
        ObserverCache _observer;
};
 
}

#endif // __OBSERVERABLE_H__

 ///
 /// @file    NewspaperOffice.h
 /// @author  marrs(chenchengxi993@gmail.com)
 /// @date    2017-08-20 20:07:02
 ///

#ifndef __NEWSPAPEROFFICE_H__
#define __NEWSPAPEROFFICE_H__

#include "Observerable.h"
 
namespace marrs{
 
class NewspaperOffice
: public Observerable
{
    public:
        void AddObserver(Observer * observer);
        void DelObserver(Observer * observer);
        void NotifyObserver(string str_message);
};
 
}

#endif // __NEWSPAPEROFFICE_H__

 ///
 /// @file    NewspaperOffice.cc
 /// @author  marrs(chenchengxi993@gmail.com)
 /// @date    2017-08-20 20:19:15
 ///
 
#include "NewspaperOffice.h"
#include "Observer.h"
#include <algorithm>

namespace marrs{

void NewspaperOffice::AddObserver(Observer * observer)
{
    cout << "add a new Reader" << endl;
    cout << "name : " << observer->GetName() << endl;
    _observer.push_back(observer);
}

void NewspaperOffice::DelObserver(Observer * observer)
{
    cout << "del a Reader" << endl;
    cout << "name : " << observer->GetName() << endl;
    _observer.erase(remove(_observer.begin(), _observer.end(), observer));
}

void NewspaperOffice::NotifyObserver(string str_message)
{
    ObserverCache::iterator it_Observer;
    it_Observer = _observer.begin();
    for(; it_Observer != _observer.end(); ++it_Observer)
    {
        (*it_Observer)->Update(str_message);
    }
}
 
}

 ///
 /// @file    Readers.h
 /// @author  marrs(chenchengxi993@gmail.com)
 /// @date    2017-08-20 20:43:46
 ///

#ifndef __READERS_H__
#define __READERS_H__

#include "Observer.h"
 
namespace marrs{
 
class Readers
: public Observer
{
    public:
        Readers(string str_name);
    public:
        void Update(string & str_message);
        string GetName();
        string GetMsg();
};

}

#endif // __READERS_H__

 ///
 /// @file    Readers.cc
 /// @author  marrs(chenchengxi993@gmail.com)
 /// @date    2017-08-20 20:46:08
 ///
 
#include "Readers.h"

namespace marrs{

Readers::Readers(string str_name)
{
    _str_name = str_name;
    _str_message = "None";
}

void Readers::Update(string & str_message)
{
    cout << "my name : " << _str_name << endl;
    cout << "recv msg: " << str_message << endl;
    _str_message = str_message;
}

string Readers::GetName()
{
    return _str_name;
}

string Readers::GetMsg()
{
    return _str_message;
}
 
}

 ///
 /// @file    Main.cc
 /// @author  marrs(chenchengxi993@gmail.com)
 /// @date    2017-08-20 20:50:17
 ///
 
#include "Readers.h"
#include "NewspaperOffice.h"

using namespace marrs;

int main()
{
    NewspaperOffice * newspaperoffice = new NewspaperOffice;
    Readers * reader1 = new Readers("zhang san");
    Readers * reader2 = new Readers("li si");
    Readers * reader3 = new Readers("wang wu");
    Readers * reader4 = new Readers("zhao liu");

    newspaperoffice->AddObserver(reader1);
    newspaperoffice->AddObserver(reader2);
    newspaperoffice->NotifyObserver("first msg");
    cout << "zhang san   msg: " << reader1->GetMsg() << endl;
    cout << "li si       msg: " << reader2->GetMsg() << endl;
    cout << "wang wu     msg: " << reader3->GetMsg() << endl;
    cout << "zhao liu    msg: " << reader4->GetMsg() << endl;


    newspaperoffice->AddObserver(reader3);
    newspaperoffice->DelObserver(reader1);
    newspaperoffice->NotifyObserver("second msg");
    cout << "zhang san   msg: " << reader1->GetMsg() << endl;
    cout << "li si       msg: " << reader2->GetMsg() << endl;
    cout << "wang wu     msg: " << reader3->GetMsg() << endl;
    cout << "zhao liu    msg: " << reader4->GetMsg() << endl;



    delete newspaperoffice;
    delete reader1;
    delete reader2;
    delete reader3;
    delete reader4;

    return 0;
}

[ccx@ubuntu ~/object-oriented/Observer_Pattern]$>g++ * -o main.exe
[ccx@ubuntu ~/object-oriented/Observer_Pattern]$>./main.exe 
add a new Reader
name : zhang san
add a new Reader
name : li si
my name : zhang san
recv msg: first msg
my name : li si
recv msg: first msg
zhang san   msg: first msg
li si       msg: first msg
wang wu     msg: None
zhao liu    msg: None
add a new Reader
name : wang wu
del a Reader
name : zhang san
my name : li si
recv msg: second msg
my name : wang wu
recv msg: second msg
zhang san   msg: first msg
li si       msg: second msg
wang wu     msg: second msg
zhao liu    msg: None