设计模式C++实现23:中介者模式（Mediator）

部分内容参考大话设计模式第25章；本实验通过C++语言实现。 

一 原理 

意图：用一个中介对象来封装一系列对象的交互，中介者使得各个对象不需要显示地相互引用，从而使耦合松散，而且可以独立地改变它们之间的交互。 

上下文：多个对象互相关联交互，对象之间维持一种复杂的网状引用关系。如果遇到一些需求更改，这种直接的引用关系将面临不断的变化。

如何管理对象间的复杂关联关系，避免相互交互的对象之间的紧耦合引用关系，从而更好地抵御变化？ 

中介者模式静态类图 

​ 

Mediator：定义一个接口与各个Colleague(同事)通信。

ConcreteMediator:通过协调各个Colleague实现协作行为,了解并维护它的各个Colleague。

Colleague：每个Colleague都知道它的Mediator对象；每个Colleague在需要与其他Colleague通信的时候，都与它的Mediator通信。

 

测试代码 

#include <iostream>
#include <list>
#include <mutex>
#include <inttypes.h>
using namespace std;
class Mediator;class Colleague
{
public:Mediator *mediator;Colleague(Mediator *);virtual void send(string msg) = 0;virtual void notify(string msg) = 0;
};class Mediator
{
public:virtual void send(Colleague *c,string msg) = 0;
};Colleague::Colleague(Mediator *m):mediator(m)
{}class ConcreteColleague1:public Colleague
{
public:ConcreteColleague1(Mediator *m):Colleague(m){}// Colleague interface
public:void send(string msg) override{this->mediator->send(this,msg);}void notify(string msg) override{cout << "同事1得到信息:" << msg << endl;}
};class ConcreteColleague2:public Colleague
{
public:ConcreteColleague2(Mediator *m):Colleague(m){}// Colleague interface
public:void send(string msg) override{this->mediator->send(this,msg);}void notify(string msg) override{cout << "同事2得到信息:" << msg << endl;}
};class ConreteMediator:public Mediator
{
public:Colleague *c1;Colleague *c2;void setC1(Colleague *value);void setC2(Colleague *value);// Mediator interface
public:void send(Colleague *c, string msg){if(c == c1){c2->notify(msg);}else{c1->notify(msg);}}
};
void ConreteMediator::setC2(Colleague *value)
{
c2 = value;
}void ConreteMediator::setC1(Colleague *value)
{c1 = value;
}int main(void)
{ConreteMediator *m = new ConreteMediator();Colleague *c1 = new ConcreteColleague1(m);Colleague *c2 = new ConcreteColleague2(m);m->setC1(c1);m->setC2(c2);c1->send("我是C1");c2->send("我是C2");return 0;
}

测试结果：

同事2得到信息:我是C1

同事1得到信息:我是C2

二 实例

 

抽象后的UML图 

 测试代码：

#include <iostream>
#include <list>
#include <mutex>
#include <inttypes.h>
using namespace std;class guojia;
//机构
class jigou{
public://传话virtual void chuanhua(string msg,guojia *g) = 0;
};
//国家
class guojia{
public:jigou *mediator;guojia(jigou *j):mediator(j){}virtual void read(string msg) = 0;virtual void write(string msg) = 0;};
//美国
class meiguo:public guojia{public:meiguo(jigou *j):guojia(j){}// guojia interface
public:void read(string msg){cout << "==>【美国收到消息】 " << msg << endl;}void write(string msg){cout << "【美国发消息】 " << msg << endl;this->mediator->chuanhua(msg,this);}
};//伊拉克
class yilake:public guojia{
public:yilake(jigou *j):guojia(j){}// guojia interface
public:void read(string msg){cout << "==>【伊拉克收到消息】 " << msg << endl;}void write(string msg){cout << "【伊拉克发消息】 " << msg << endl;this->mediator->chuanhua(msg,this);}
};class anlihui :public jigou{
public:meiguo *g1;yilake *g2;// jigou interface
public:void chuanhua(string msg,guojia *g){if(g == g1){g2->read(msg);}else{g1->read(msg);}}void setG1(meiguo *value);void setG2(yilake *value);
};
void anlihui::setG2(yilake *value)
{
g2 = value;
}void anlihui::setG1(meiguo *value)
{
g1 = value;
}int main(void)
{anlihui *m = new anlihui();meiguo *g1 = new meiguo(m);yilake *g2 = new yilake(m);m->setG1(g1);m->setG2(g2);g1->write("地球是方的，跟我念");g2->write("地球是芳芳的");g1->write("芳芳是谁？");g2->write("没有芳芳");g1->write("交出芳芳，保你荣华富贵");g2->write("真没有芳芳");return 0;}

运行结果： 

【美国发消息】 地球是方的，跟我念

==>【伊拉克收到消息】 地球是方的，跟我念

【伊拉克发消息】 地球是芳芳的

==>【美国收到消息】 地球是芳芳的

【美国发消息】 芳芳是谁？

==>【伊拉克收到消息】 芳芳是谁？

【伊拉克发消息】 没有芳芳

==>【美国收到消息】 没有芳芳

【美国发消息】 交出芳芳，保你荣华富贵

==>【伊拉克收到消息】 交出芳芳，保你荣华富贵

【伊拉克发消息】 真没有芳芳

==>【美国收到消息】 真没有芳芳

小结