Chain of Responsibility职责链[通俗易懂]

#include<bits/stdc++.h>
#include<string>

using namespace std;

enum class RequestType{ 
   
    REQ_HANDLER1,
    REQ_HANDLER2,
    REQ_HANDLER3
}
class Request{ 
   
    string description;
    RequestType reqType;
public:
    Request(const string&desc,Request type) : description(desc),reqType()
    RequestType getReqType()const { 
   return reqType;}

    const string& getDescription()const { 
   return description;}
}

class ChainHandler{ 
   
    ChainHandler *nextChain;
    void sendRequestToNextHandler(const Request &req){ 
   
        if(nextChain != nullptr){ 
   
            nextChain->handle(req);
        }
    }
protected:
    virtual bool canHandleRequest(const Request& req) = 0;
    virtual bool processRequest(const Request& req) = 0;
public:
    ChainHandler(){ 
   nextChain = nullptr;}
    void setNextChain(ChainHandler * next){ 
   nextChain = next;}
    
    void handle(const Request& req){ 
   
        if(canHandleRequest(req))
            processRequest(req);
        else
            sendRequestToNextHandler(req);
    }
}

class Handler1 : public ChainHandler{ 
   
protected:
    bool canHandlerRequest(const Request&req)override{ 
   
        return req.getReqType() == RequestType::REQ_HANDLER1;
    }
    void processRequest(const Request&req)override{ 
   
        cout << "Handler1 is handle request" << req.getDescription() << endl;
    }
};
class Handler2 : public ChainHandler{ 
   
protected:
    bool canHandlerRequest(const Request&req)override{ 
   
        return req.getReqType() == RequestType::REQ_HANDLER2;
    }
    void processRequest(const Request&req)override{ 
   
        cout << "Handler2 is handle request" << req.getDescription() << endl;
    }
};
class Handler3 : public ChainHandler{ 
   
protected:
    bool canHandlerRequest(const Request&req)override{ 
   
        return req.getReqType() == RequestType::REQ_HANDLER3;
    }
    void processRequest(const Request&req)override{ 
   
        cout << "Handler3 is handle request" << req.getDescription() << endl;
    }
};

int main(){ 
   
    Handler1 h1;
    Handler1 h2;
    Handler1 h3;
    h1.setNextChain(&h2);
    h2.setNextChain(&h3);
    Request req("process task ... ",RequestType::REQ_HANDLER3);
    h1.handle(req);
    return 0;
}