DP: Chain of Responsibility

This pattern passes a request along a chain of handlers until one of them handles it.

Used in interrupt handling, event pipelines, middleware, and packet processing.

  • Decouples sender from receiver chain
  • Flexible processing pipelines

C Example

c 
#include <stdio.h>

void handlerA(int req) {
    if(req < 10) printf("Handled by A\n");
}

void handlerB(int req) {
    if(req >= 10) printf("Handled by B\n");
}

int main() {
    int request = 15;
    handlerA(request);
    handlerB(request);
}

C++ Example

cpp 
#include <iostream>
using namespace std;

class Handler {
protected:
    Handler* next = nullptr;
public:
    void setNext(Handler* n){ next = n; }
    virtual void handle(int req){
        if(next) next->handle(req);
    }
};

class SmallHandler : public Handler {
public:
    void handle(int req) override {
        if(req < 10) cout<<"Small handled\n";
        else Handler::handle(req);
    }
};

class LargeHandler : public Handler {
public:
    void handle(int req) override {
        if(req >= 10) cout<<"Large handled\n";
    }
};

int main() {
    SmallHandler s; LargeHandler l;
    s.setNext(&l);

    s.handle(15);
}