中介者模式
定义
+ 用一个中介对象来封装一系列的对象交互。中介者使各个对象不需要显示地互相引用，从而使耦合松散，并且可以独立地改变他们的交互。
UML 类图
使用场景
+ 一般用于一组对象以定义良好但复杂的方式进行通信的场景，比如窗体的 Form 或者 web 页面 asp
+ 想定制一个分布在多个类中的行为，但是又不想生成太多的子类的场合。
代码
/**
* 中介者模式：用一个中介对象封装一系列的对象交互
* 中介者使各对象不需要显示地互相引用，从而使其耦合松散
* 而且可以独立地改变他们之间的交互
*/
#include <iostream>
#include <string>
using namespace std;
class Colleague;
class Mediator
{
public:
virtual void send(string message, Colleague* colleague) = 0;
};
class Colleague
{
public:
Colleague(Mediator *p_mediator): m_pMediator(p_mediator){}
virtual void send(string message) = 0;
protected:
Mediator* m_pMediator;
};
class ConcreteColleague1 : public Colleague
{
public:
ConcreteColleague1(Mediator* p_mediator):Colleague(p_mediator){}
virtual void send(string message){
m_pMediator->send(message, this);
}
void notify(string messsage){
cout << "Colleague 1 has received message: " << messsage << endl;
}
};
class ConcreteColleague2 : public Colleague
{
public:
ConcreteColleague2(Mediator* p_mediator):Colleague(p_mediator){}
virtual void send(string message){
m_pMediator->send(message, this);
}
void notify(string messsage){
cout << "Colleague 2 has received message: " << messsage << endl;
}
};
class ConcreteMediator : public Mediator
{
public:
virtual void send(string message, Colleague* p_struColleague){
ConcreteColleague1* p_struConcreteColleague1 = dynamic_cast<ConcreteColleague1*>(p_struColleague);
if(p_struConcreteColleague1){
cout << "The message from Colleague1: " << message << endl;
if(m_pstruColleague_2){
m_pstruColleague_2->notify(message);
}
}
else{
cout << "The message from Colleague2: " << message << endl;
if(m_pstruColleague_1){
m_pstruColleague_1->notify(message);
}
}
}
void setColleague1(Colleague* p_struColleague){
m_pstruColleague_1 = dynamic_cast<ConcreteColleague1*>(p_struColleague);
}
void setColleague2(Colleague* p_struColleague){
m_pstruColleague_2 = dynamic_cast<ConcreteColleague2*>(p_struColleague);
}
private:
ConcreteColleague1* m_pstruColleague_1;
ConcreteColleague2* m_pstruColleague_2;
};
int main() {
Mediator* p_struMediator = new ConcreteMediator();
Colleague* p_struColleague_1 = new ConcreteColleague1(p_struMediator);
Colleague* p_struColleague_2 = new ConcreteColleague2(p_struMediator);
ConcreteMediator* p_struConcreteMediator = dynamic_cast<ConcreteMediator*>(p_struMediator);
p_struConcreteMediator->setColleague1(p_struColleague_1);
p_struConcreteMediator->setColleague2(p_struColleague_2);
string message1 = "Have you eat morning?";
p_struColleague_1->send(message1);
string message2 = "No, I haven't!";
p_struColleague_2->send(message2);
return 0;
}
优缺点
优点
+ 减少了系统的耦合性，使得子类之间的交互转换成中介类的逻辑，使逻辑集中化
缺点
+ 当系统出现多对多的对象群时，中介者模式的逻辑将会非常复杂。