c++ 行为型模式-中介者(Mediator)

1) 意图

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相互应用，从而使其耦合松散，并且可以独立地改变它们之间的交互

2) 结构

 

 其中：

1. Mediator定义一个接口用于各同事对象的通信
2. ConcreteMediator 通过协调各个Colleague 类对象实现协助行为
3. Colleague 知道它的中介者对象，每个Colleague 类对象在需要与其他Colleague 通信的时候与它的中介者通信

3) 适用性

1. 一组对象通信方式复杂，产生的相互依赖关系结构混乱且难以理解
2. 一个对象引用其他很多对象并且直接与这些对象通信，导致难以复用该对象
3. 想定制一个分布在多个类中的行为，而又不想生成太多的子类

4) 举例

 1 #include <iostream>
 2 //ConcreteColleague1和ConcreteColleague2互相发消息，让对方通知出去,为减小其耦合，通过中介者Mediator实现这一功能 
 3 class Mediator;
 4 class Colleague
 5 {
 6 public:
 7     Colleague(Mediator* pMediator):m_pMediator(pMediator){}
 8     virtual ~Colleague() {}
 9     virtual void send(std::string msg) = 0;
10 protected:
11     Mediator* m_pMediator;
12 };
13 class ConcreteColleague1:public Colleague
14 {
15 public:
16     ConcreteColleague1(Mediator* pMediator) :Colleague(pMediator) {}
17     virtual ~ConcreteColleague1() {}
18     virtual void send(std::string msg);
19     void notify(std::string msg)
20     {
21         std::cout <<" ConcreteColleague1 notify "<< msg.c_str() << std::endl;
22     }
23 };
24 class ConcreteColleague2 :public Colleague
25 {
26 public:
27     ConcreteColleague2(Mediator* pMediator) :Colleague(pMediator) {}
28     virtual ~ConcreteColleague2() {}
29     virtual void send(std::string msg);
30     void notify(std::string msg)
31     {
32         std::cout <<" ConcreteColleague2 notify "<< msg.c_str() << std::endl;
33     }
34 };
35 class Mediator
36 {
37 public:
38     Mediator() {}
39     virtual ~Mediator() {}
40     virtual void send(std::string msg, Colleague* pColleague) = 0;
41     virtual void setColleague1(Colleague* pColleague) = 0;
42     virtual void setColleague2(Colleague* pColleague) = 0;
43 
44 };
45 
46 class ConcreteMediator:public Mediator
47 {
48 public:
49     ConcreteMediator() {};
50     virtual ~ConcreteMediator() {}
51     void send(std::string msg, Colleague* pColleague)
52     {
53         ConcreteColleague1* pConcreteColleague1 =
54             dynamic_cast<ConcreteColleague1*>(pColleague);
55         if (pConcreteColleague1)
56         {
57             std::cout << "msg from ConcreteColleague1" << std::endl;
58             m_pColleague2->notify(msg);
59         }
60         else
61         {
62             std::cout << "msg from ConcreteColleague2" << std::endl;
63             m_pColleague1->notify(msg);
64         }
65     }
66     virtual void setColleague1(Colleague* pColleague)
67     {
68         m_pColleague1 = dynamic_cast<ConcreteColleague1*>(pColleague);
69     }
70     virtual void setColleague2(Colleague* pColleague)
71     {
72         m_pColleague2 = dynamic_cast<ConcreteColleague2*>(pColleague);
73     }
74 private:
75     ConcreteColleague1* m_pColleague1;
76     ConcreteColleague2* m_pColleague2;
77 };
78 
79 void ConcreteColleague1::send(std::string msg)
80 {
81     m_pMediator->send(msg,this);
82 }
83 void ConcreteColleague2::send(std::string msg)
84 {
85     m_pMediator->send(msg, this);
86 }
87 int main() 
88 {
89     Mediator* pMediator = new ConcreteMediator();
90     Colleague* pColleague1 = new ConcreteColleague1(pMediator);
91     Colleague* pColleague2 = new ConcreteColleague2(pMediator);
92     pMediator->setColleague1(pColleague1);
93     pMediator->setColleague2(pColleague2);
94 
95     pColleague1->send("hello");
96     pColleague2->send("world");
97     system("pause");
98 }