C++模式学习------代理模式

Proxy代理模式 ：

为其他对象提供一种代理以控制对这个对象的访问。代理类作为桥梁是请求方和执行方的中间者，将请求方和真正的执行方分割开来，也是两者之间调用的协调者。例如执行类也就是被代理类，可以在不考虑各种特殊条件下提供所有的执行方法，请求者也可以不考虑特殊条件提出所有的请求。而在调用和被调用时需要考虑的所有条件，在代理类中完成。

1. 考虑请求方的情况：由各代理处理不同的请求

 class Service
 {
 public:
     Service();

     virtual void serviceLv0() = ;
     virtual void serviceLv1() = ;
     virtual void serviceLv2() = ;
 };

 class OfferService : public Service
         //真正的服务提供者
 {
 public:
     OfferService();

     void serviceLv0()
     {
         cout<<"Offer serviceLv0"<<endl;
     }
     void serviceLv1()
     {
         cout<<"Offer serviceLv0"<<endl;
     }
     void serviceLv2()
     {
         cout<<"Offer serviceLv0"<<endl;
     }
 };

 class ProxyOfferServiceLv0 : public Service
         //lv0 的服务提供代理
 {
 public:
     ProxyOfferServiceLv0()
     {
         m_instance = new OfferService();
     }

     void serviceLv0()
     {
         m_instance->serviceLv0();
     }
     void serviceLv1()
     {
         cout<<"No serviceLv0"<<endl;
     }
     void serviceLv2()
     {
         cout<<"No serviceLv0"<<endl;
     }

     OfferService* m_instance;
 };

 class ProxyOfferServiceLv2 : public Service
         //lv2 的服务提供代理
 {
 public:
     ProxyOfferServiceLv2()
     {
         m_instance = new OfferService();
     }

     void serviceLv0()
     {
         m_instance->serviceLv0();
     }
     void serviceLv1()
     {
         m_instance->serviceLv1();
     }
     void serviceLv2()
     {
         m_instance->serviceLv2();
     }

     OfferService* m_instance;
 };

2. 考虑执行方的情况

 enum EnumState
 {
     State_isOK,
     State_notOK
 };

 class Service
 {
 public:
     Service();

     virtual void serviceLv0() = ;
     virtual void serviceLv1() = ;
     virtual void serviceLv2() = ;

     int getServiceState()
     {
         return m_state;
     }

     int m_state; // EnumState
 };

 class OfferService : public Service
         //真正的服务提供者
 {
 public:
     OfferService();

     void serviceLv0()
     {
         cout<<"Offer serviceLv0"<<endl;
     }
     void serviceLv1()
     {
         cout<<"Offer serviceLv0"<<endl;
     }
     void serviceLv2()
     {
         cout<<"Offer serviceLv0"<<endl;
     }
 };

 class ProxyOfferServiceLv0 : public Service
         //lv0 的服务提供代理
 {
 public:
     ProxyOfferServiceLv0()
     {
         m_instance = new OfferService();
     }

     void serviceLv0()
     {
         if(m_instance->getServiceState() == State_isOK)
             //查看执行方的状态
         {
             m_instance->serviceLv0();
         }
         else
         {
             cout<<"serviceLv0 is noOK"<<endl;
         }
     }
     void serviceLv1()
     {
         cout<<"No serviceLv0"<<endl;
     }
     void serviceLv2()
     {
         cout<<"No serviceLv0"<<endl;
     }

     OfferService* m_instance;
 };

 class ProxyOfferServiceLv2 : public Service
         //lv2 的服务提供代理
 {
 public:
     ProxyOfferServiceLv2()
     {
         m_instance = new OfferService();
     }

     void serviceLv0()
     {
         if(m_instance->getServiceState() == State_isOK)
             //查看执行方的状态
         {
             m_instance->serviceLv0();
         }
         else
         {
             cout<<"serviceLv0 is noOK"<<endl;
         }
     }
     void serviceLv1()
     {
         if(m_instance->getServiceState() == State_isOK)
             //查看执行方的状态
         {
             m_instance->serviceLv1();
         }
         else
         {
             cout<<"serviceLv1 is noOK"<<endl;
         }
     }
     void serviceLv2()
     {
         if(m_instance->getServiceState() == State_isOK)
             //查看执行方的状态
         {
             m_instance->serviceLv2();
         }
         else
         {
             cout<<"serviceLv2 is noOK"<<endl;
         }
     }

     OfferService* m_instance;
 };