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() = 0;
    virtual void serviceLv1() = 0;
    virtual void serviceLv2() = 0;
};

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() = 0;
    virtual void serviceLv1() = 0;
    virtual void serviceLv2() = 0;

    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;
};