设计模式之中介者模式（Mediator）的C++实现

1、中介者模式的提出

在软件组件开发过程中，如果存在多个对象，且这些对象之间存在的相互交互的情况不是一一对应的情况，这种功能组件间的对象引用关系比较复杂，耦合度较高。如果有一些新的需求变化，则不易扩展。中介者模式可以解决这种问题。中介者模式使用一个“中介对象”去管理对象间的关联关系，这个中介对象里面定义了对象间的数据统一交互接口，解耦对象间的直接交互依赖，从而提高代码的扩展性。

2、需求描述

有2个线上人员，这两个线上人员可以相互发送和接收对象的消息。设计一个线上人员数据交互的代码，且代码架构便于扩展。

3、中介者模式的代码实现

（1）UML图如下：

 

 （2）代码实现如下：

#include 
#include 

class Mediator;
class OnlinerPeople
{
protected:
    Mediator* mediator;
public:
    virtual void sendMsg(std::string msg)=0;
    virtual void receiveMsg(std::string msg)=0;
    virtual ~OnlinerPeople(){};
};

class Mediator
{
protected:
    std::vectorvecOnlinePeoples;
public:
    virtual void sendMessage(std::string msg,OnlinerPeople* pepole)=0;
    virtual void addOnliners(OnlinerPeople* people)=0;
    virtual ~Mediator(){};
};

class ConcreteMediator:public Mediator
{
public:
    void addOnliners(OnlinerPeople* people)override
    {
        vecOnlinePeoples.emplace_back(people);
    };

    virtual void sendMessage(std::string msg, OnlinerPeople *pepole) override
    {
        for(auto it =  vecOnlinePeoples.begin();it != vecOnlinePeoples.end(); it++)
        {
            if( *it != pepole)
            {
               (*it)->receiveMsg(msg);
            }
        }
    }
};



class OnlinerPeople1:public OnlinerPeople
{
public:
    void Init(Mediator* mediator){
        this->mediator = mediator;
    }

    virtual void sendMsg(std::string msg) override
    {
        std::cout << "OnlinerPeople1 sendMsg: " << std::endl;
        mediator->sendMessage(msg,this);
    }

    virtual void receiveMsg(std::string msg) override
    {
        std::cout << "OnlinerPeople1 receive msg: " << msg << std::endl;
    }
};

class OnlinerPeople2:public OnlinerPeople
{
public:
    void Init(Mediator* mediator){
        this->mediator = mediator;
    }

    virtual void sendMsg(std::string msg) override
    {
        std::cout << "OnlinerPeople2 sendMsg: " << std::endl;
        mediator->sendMessage(msg,this);
    }

    virtual void receiveMsg(std::string msg) override
    {
        std::cout << "OnlinerPeople2 receive msg: " << msg << std::endl;
    }
};
class Client
{
private:
    Mediator* mediator{nullptr};
    OnlinerPeople1 people1;
    OnlinerPeople2 people2;
public:
    Client(Mediator* p){
        mediator = p;
        people1.Init(mediator);
        people2.Init(mediator);
     };
    void DoWork()
    {
        mediator->addOnliners(&people1);
        mediator->addOnliners(&people2);
        people1.sendMsg("hello people2");
        people2.sendMsg("hello people1");
    };
};

int main()
{
    Mediator* mediator = new ConcreteMediator();
    Client obj(mediator);
    obj.DoWork();

    delete mediator;
    mediator = nullptr;
    return 0;
}

 程序运行结果如下：