c++中介者模式

1.中介者模式简介

   中介者模式（Mediator Pattern）是用来降低多个对象和类之间的通信复杂性。这种模式提供了一个中介类，该类通常处理不同类之间的通信，并支持松耦合，使代码易于维护。

2.源码实现

#include <iostream>
#include <string>

using namespace std;

#define SAFE_DELETE(p) if(p) {delete p; p = NULL}

class Mediator;

class Colleague
{
public:
    Colleague(Mediator *pMediator) : m_pMediator(pMediator){};
    virtual void Send(char *message) = 0;

protected:
    Mediator *m_pMediator;
};

class ConcreteColleague1 : public Colleague
{
public:
    ConcreteColleague1(Mediator *pMediator) : Colleague(pMediator){};

    virtual void Send(char *message);

    void Notify(char *message)
    {
        cout << message << endl;
    }
};

class ConcreteColleague2 : public Colleague
{
public:
    ConcreteColleague2(Mediator *pMediator) : Colleague(pMediator){};

    virtual void Send(char *message);

    void Notify(char *message)
    {
        cout << "ConcreteColleague2 is handling the message." << endl;
        cout << message << endl;
    }
};

class Mediator
{
public:
    virtual void Sent(char *message, Colleague *pColleague) = 0;
};

void ConcreteColleague1::Send(char *message)
{
    m_pMediator->Sent(message, this);
}

void ConcreteColleague2::Send(char *message)
{
    m_pMediator->Sent(message, this);
}

class ConcreteMediator : public Mediator
{
public:
    void Sent(char *message, Colleague *pColleague)
    {
        ConcreteColleague1 *pConcreteColleague1 = dynamic_cast<ConcreteColleague1 *>(pColleague);

        if(pConcreteColleague1)
        {
            cout << "The message is from ConcreteColleague1" << endl;

            if(m_pColleague2)
            {
                m_pColleague2->Notify(message);
            }
        }
        else
        {
            if(m_pColleague1)
            {
                m_pColleague1->Notify(message);
            }
        }
    }

    void setColleague1(Colleague *pColleague)
    {
        m_pColleague1 = dynamic_cast<ConcreteColleague1 *>(pColleague);
    }

    void setColleague2(Colleague *pColleague)
    {
        m_pColleague2 = dynamic_cast<ConcreteColleague2 *>(pColleague);
    }

private:
     ConcreteColleague1 *m_pColleague1;
     ConcreteColleague2 *m_pColleague2;
};

int main(int argc, char **argv)
{
    Mediator *pMediator = new ConcreteMediator();

    Colleague *pColleague1 = new ConcreteColleague1(pMediator);
    Colleague *pColleague2 = new ConcreteColleague2(pMediator);

    ConcreteMediator *pConcreteMediator = dynamic_cast<ConcreteMediator *>(pMediator);
    pConcreteMediator->setColleague1(pColleague1);
    pConcreteMediator->setColleague2(pColleague2);

    char message[128] = "Where are you from?";

    pColleague1->Send(message);

    delete pColleague1;
    delete pColleague2;
    delete pMediator;

    return 0;
}

3.编译源码

$ g++ -o example example.cpp

4.运行及其结果

$ ./example
The message is from ConcreteColleague1
ConcreteColleague2 is handling the message.
Where are you from?