设计模式C++描述----05.职责链(Chain of Responsibility)模式

一. 概述

职责链模式：

使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。将这些对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止。

二. 举个例子

员工要求加薪

公司的管理者一共有三级：总经理、总监、经理，如果一个员工要求加薪，应该向主管的经理申请，如果加薪的数量在经理的职权内，那么经理可以直接批准，否则将申请上交给总监。总监的处理方式也一样，总经理可以处理所有请求。这就是典型的职责链模式，请求的处理形成了一条链，直到有一个对象处理请求。

结构图如下：

假设：

经理可以处理薪水的范围在：0~500
总监可以处理薪水的范围在：500~1000
总经理可以处理薪水的范围在：1000~2000

则代码如下：

[cpp] //////////////////////////////////////////////////////////////////////////
//抽象处理类
class Handle
{
public:
    virtual ~Handle()
    {
        delete _succ;
    }

    virtual void HandleRequest(int request) = 0;

    //设置其上级
    void SetSuccessor(Handle* succ)
    {
        _succ = succ;
    }

    Handle* GetSuccessor()
    {
        return _succ;
    }

protected:
    Handle()
    {
        _succ = NULL;
    }

private:
    Handle* _succ;
};

//具体处理类 A
class ConcreteHandleA: public Handle
{
public:
    void HandleRequest(int request)
    {
        if (request >= 0 && request < 500)
        {
            cout << "ConcreteHandleA deal with: " << request <<endl;
        }
        else if (this->GetSuccessor() != NULL)
        {
            this->GetSuccessor()->HandleRequest(request);
        }
        else
        {
            cout << "Can't deal with " << request << endl;
        }
    }
};

//具体处理类 B
class ConcreteHandleB: public Handle
{
public:
    void HandleRequest(int request)
    {
        if (request >= 500 && request < 1000)
        {
            cout << "ConcreteHandleB deal with: " << request <<endl;
        }
        else if (this->GetSuccessor() != NULL)
        {
            this->GetSuccessor()->HandleRequest(request);
        }
        else
        {
            cout << "Can't deal with " << request << endl;
        }
    }
};

//具体处理类 C
class ConcreteHandleC: public Handle
{
public:
    void HandleRequest(int request)
    {
        if (request >= 1000 && request < 2000)
        {
            cout << "ConcreteHandleC deal with: " << request <<endl;
        }
        else if (this->GetSuccessor() != NULL)
        {
            this->GetSuccessor()->HandleRequest(request);
        }
        else
        {
            cout << "Can't deal with " << request << endl;
        }
    }
};

//////////////////////////////////////////////////////////////////////////
//测试
int main()
{
    Handle* h1 = new ConcreteHandleA();
    Handle* h2 = new ConcreteHandleB();
    Handle* h3 = new ConcreteHandleC();

    //设置其上级
    h1->SetSuccessor(h2);
    h2->SetSuccessor(h3);

    h1->HandleRequest(300);
    h1->HandleRequest(600);
    h1->HandleRequest(1500);
    h1->HandleRequest(3000);

    delete h1;
    delete h2;
    delete h3;

    return 0;
}
//////////////////////////////////////////////////////////////////////////
//抽象处理类
class Handle
{
public:
virtual ~Handle()
{
  delete _succ;
}

virtual void HandleRequest(int request) = 0;

//设置其上级 www.zzzyk.com
void SetSuccessor(Handle* succ)
{
_succ = succ;
}

Handle* GetSuccessor()
{
return _succ;
}

protected:
Handle()
{
_succ = NULL;
}

private:
Handle* _succ;
};

//具体处理类 A
class ConcreteHandleA: public Handle
{
public:
void HandleRequest(int request)
{
if (request >= 0 && request <

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