23种设计模式(18)--Mediator模式

使用了Mediator模式，原来在各个对象内部所做的事情，现在全部移交到Mediator里了。也就是将分布在各个对象里面的协议处理过程，全部统一放在Mediator里去做了。骤看来，好像我们是把职责转移了，但是对于代码逻辑的清晰却有很大的好处，这个模式让我们能专注于各个对象之间的交互（他们的交互都放在Mediator类里去做了）。Mediator的核心思想就是把错综复杂的类间的关系独立出来，使得他们的关系清晰化。这样做的好处是如果类间的交互协议有变化，则只修改Mediator类就行了，但是它的缺点也在于Mediator类，因为所有的交互都转移到Mediator中，他的复杂性可想而知，搞不好会变成一个庞然大物，难以维护。

Mediator模式结构图：

代码实现：

#include "iostream"#include <string>using namespace std;class Mediator {public:virtual ~Mediator(){};virtual void DoActionFromAtoB() = 0;virtual void DoActionFromBtoA() = 0;protected:Mediator(){};private:};class Colleage{public:virtual ~Colleage(){};virtual void Aciton() = 0;virtual void SetState(const string& sdt) = 0;virtual string GetState() = 0; protected: Colleage();Colleage(Mediator* mdt);Mediator* _mdt;private:};class ConcreteColleageA :public Colleage{public:ConcreteColleageA(){};ConcreteColleageA(Mediator* mdt);~ConcreteColleageA(){};void Aciton();void SetState(const string& sdt);string GetState();protected:private:string _sdt;};class ConcreteColleageB :public Colleage{public:ConcreteColleageB(){};ConcreteColleageB(Mediator* mdt);~ConcreteColleageB(){};void Aciton();void SetState(const string& sdt);string GetState();protected:private:string _sdt;};Colleage::Colleage(Mediator* mdt){this->_mdt = mdt;}ConcreteColleageA::ConcreteColleageA(Mediator* mdt) :Colleage(mdt){}string ConcreteColleageA::GetState(){return _sdt;}void ConcreteColleageA::SetState(const string& sdt){_sdt = sdt;}void ConcreteColleageA::Aciton(){this->_mdt->DoActionFromAtoB();cout << "State of ConcreteColleageB:" << " " << this->GetState() << endl;}ConcreteColleageB::ConcreteColleageB(Mediator* mdt) :Colleage(mdt){}void ConcreteColleageB::Aciton(){this->_mdt->DoActionFromBtoA();cout << "State of ConcreteColleageB:" << " " << this->GetState() << endl;}string ConcreteColleageB::GetState(){return _sdt;}void ConcreteColleageB::SetState(const string& sdt){_sdt = sdt;}class ConcreteMediator :public Mediator{public:ConcreteMediator(){};ConcreteMediator(Colleage* clgA, Colleage* clgB);~ConcreteMediator(){};void SetConcreteColleageA(Colleage* clgA);void SetConcreteColleageB(Colleage* clgB);Colleage* GetConcreteColleageA();Colleage* GetConcreteColleageB();void IntroColleage(Colleage* clgA, Colleage* clgB);void DoActionFromAtoB();void DoActionFromBtoA();protected:private:Colleage* _clgA;Colleage* _clgB;};ConcreteMediator::ConcreteMediator(Colleage* clgA, Colleage* clgB){this->_clgA = clgA;this->_clgB = clgB;}void ConcreteMediator::DoActionFromAtoB(){_clgB->SetState(_clgA->GetState());}void ConcreteMediator::SetConcreteColleageA(Colleage* clgA){this->_clgA = clgA;}void ConcreteMediator::SetConcreteColleageB(Colleage* clgB){this->_clgB = clgB;}Colleage* ConcreteMediator::GetConcreteColleageA(){return _clgA;}Colleage* ConcreteMediator::GetConcreteColleageB(){return _clgB;}void ConcreteMediator::IntroColleage(Colleage* clgA, Colleage* clgB){this->_clgA = clgA;this->_clgB = clgB;}void ConcreteMediator::DoActionFromBtoA(){_clgA->SetState(_clgB->GetState());}int main(int argc, char* argv[]){ConcreteMediator* m = new ConcreteMediator();ConcreteColleageA* c1 = new ConcreteColleageA(m);ConcreteColleageB* c2 = new ConcreteColleageB(m);m->IntroColleage(c1, c2);c1->SetState("old");c2->SetState("old");c1->Aciton();c2->Aciton();cout << endl;c1->SetState("new");c1->Aciton();c2->Aciton();cout << endl;return 0;}