设计模式-行为-Mediator（中介者）模式

对象之间的交互是一种非常普遍的需求。当系统规模较大、对象数量众多时，相互通信的复杂度会急剧上升。为了管理这种复杂性，需要引入一个专门负责协调交互的通信类，这正是 Mediator（中介者）模式的核心思想，它同时也带来了系统间对象的松耦合。

Mediator 模式的价值在于：它将对象间的通信封装到一个独立的类中，把原本的多对多通信关系转换为一对多，从而显著降低了通信的复杂性。借助 Mediator，各个 Colleague 无需直接维护彼此的通信对象和协议，系统耦合度大幅下降，Mediator 与 Colleague 也可以相互独立地演进和修改。

此外，Mediator 模式还具备集中控制的特点，便于统一管理，也符合面向对象设计中每个类单一职责的原则。

示例代码

头文件
#pragma  once
#include "PublicHeaders.h"

class Mediator;


class Colleague
{
public:
	virtual void Action() = 0;

protected:
	Mediator *_mediator;
	friend class ConCreateMediator;
	virtual void Sync() = 0;

};

class ConCreateColleagueA :public Colleague
{
public:
	ConCreateColleagueA(Mediator*m);
	virtual void Action()override;
private:

	virtual void Sync()override;
};

class ConCreateColleagueB :public Colleague
{
public:
	ConCreateColleagueB(Mediator*m);
	virtual void Action()override;
private:

	virtual void Sync()override;
};



class Mediator
{
public:
	virtual void IntroColleague(Colleague*a, Colleague *b) = 0;
	virtual void DoActionFromAtoB() = 0;
	virtual void DoActionFromBtoA() = 0;


protected:
	Colleague *colleague_A;
	Colleague *colleague_B;


};


class ConCreateMediator :public Mediator
{
public:
	virtual void IntroColleague(Colleague*a, Colleague *b)override;
	virtual void DoActionFromAtoB()override;
	virtual void DoActionFromBtoA()override;

};



void testMediator();




源文件
#include "Mediator.h"




ConCreateColleagueA::ConCreateColleagueA(Mediator*m)
{
	this->_mediator = m;
}
void ConCreateColleagueA::Action()
{
	this->_mediator->DoActionFromAtoB();
}


void  ConCreateColleagueA::Sync()
{
	cout << __FUNCTION__ << endl;
}


ConCreateColleagueB::ConCreateColleagueB(Mediator*m)
{
	this->_mediator = m;
}
void  ConCreateColleagueB::Action()
{
	this->_mediator->DoActionFromBtoA();
}

void ConCreateColleagueB::Sync()
{
	cout << __FUNCTION__ << endl;
}






void  ConCreateMediator::IntroColleague(Colleague*a, Colleague *b)
{
	this->colleague_A = a;
	this->colleague_B = b;
}
void ConCreateMediator::DoActionFromAtoB()
{
	colleague_B->Sync();
}
void  ConCreateMediator::DoActionFromBtoA()
{
	colleague_A->Sync();
}




void testMediator()
{
	ConCreateMediator* mediator = new ConCreateMediator;

	ConCreateColleagueA *a = new ConCreateColleagueA(mediator);
	ConCreateColleagueB *b = new ConCreateColleagueB(mediator);
	mediator->IntroColleague(a, b);

	a->Action();
	b->Action();
	a->Action();



}