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 <iostream>
#include <vector>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::vector<OnlinerPeople*>vecOnlinePeoples;
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：