gistfile1.cpp

#include <stdio.h>

class Message;
class MoveMessage;
class StopMessage;

class MessageVisitor {
public:
  virtual int visit(MoveMessage &msg) = 0;
  virtual int visit(StopMessage &msg) = 0;
};


class Message {
public:
  virtual int accept(MessageVisitor *visitor) = 0;
};

class MoveMessage: public Message {
public:
  int x;
  int y;
  MoveMessage(int x,int y): x(x), y(y) {
  }

  
  virtual int accept(MessageVisitor *visitor) {
    return visitor->visit(*this);
  }
};

class StopMessage: public Message {
public:
  StopMessage() {}

  virtual int accept(MessageVisitor *visitor) {
    return visitor->visit(*this);
  }
};

class AcceptMessage: public MessageVisitor {
public:
  AcceptMessage() {};
  
  virtual int visit(MoveMessage &msg) {
    printf("Moving to x:%d, y:%d\n", msg.x, msg.y);
    return 0;
  };

  virtual int visit(StopMessage &msg) {
    printf("Stopping\n");
    return 0;
  }
};

int acceptMessage(Message* msg) {
  static AcceptMessage vstr;
  msg->accept(&vstr);
}


int main (int argc, char** argv) {
  MoveMessage m(20, 20);
  MoveMessage m2(10, 10);
  StopMessage m3;
  acceptMessage(&m);
  acceptMessage(&m2);
  acceptMessage(&m3);
  return 0;
}

int acceptMessage(const Message &msg) {
static AcceptMessage vstr;
Message *msg2 = (Message *)&msg;
msg2->accept(&vstr);
}

int main (int argc, char** argv) {
acceptMessage(MoveMessage(20, 20));
acceptMessage(MoveMessage(10, 10));
acceptMessage(StopMessage());
return 0;
}

int acceptMessage(const Message &msg) {
static AcceptMessage vstr;
Message *msg2 = (Message *)&msg;
return msg2->accept(&vstr);
}