design-patterns-cpp/mediator/Mediator.cpp

/*
 * C++ Design Patterns: Mediator
 * Author: Jakub Vojvoda [github.com/JakubVojvoda]
 * 2016
 *
 * Source code is licensed under MIT License
 * (for more details see LICENSE)
 *
 */

#include <iostream>
#include <vector>

class Mediator;

/*
 * Colleague classes
 * each colleague communicates with its mediator whenever
 * it would have otherwise communicated with another colleague
 */
class Colleague {
public:
  Colleague(Mediator *m, unsigned int i)
    : mediator(m), id(i) {}

  virtual ~Colleague() {}

  unsigned int getID() {
    return id;
  }

  virtual void send(std::string) = 0;
  virtual void receive(std::string) = 0;

protected:
  Mediator *mediator;
  unsigned int id;
};

class ConcreteColleague : public Colleague {
public:
  ConcreteColleague(Mediator *m, unsigned int i)
    : Colleague(m, i) {}

  void send(std::string msg);

  void receive(std::string msg) {
    std::cout << "Message '" << msg << "' received by Colleague " << id << std::endl;
  }
};

/*
 * Mediator
 * defines an interface for communicating with Colleague objects
 */
class Mediator {
public:
  virtual ~Mediator() {}

  virtual void add(Colleague *c) = 0;
  virtual void distribute(Colleague *sender, std::string msg) = 0;

protected:
  Mediator() {}
};

/*
 * Concrete Mediator
 * implements cooperative behavior by coordinating Colleague objects
 * and knows its colleagues
 */
class ConcreteMediator : public Mediator {
public:
  ~ConcreteMediator() {
    for (unsigned int i = 0; i < colleagues.size(); i++) {
      delete colleagues[i];
    }
    colleagues.clear();
  }

  void add(Colleague *c) {
    colleagues.push_back(c);
  }

  void distribute(Colleague *sender, std::string msg) {
    for (unsigned int i = 0; i < colleagues.size(); i++) {
      if (colleagues.at(i)->getID() != sender->getID()) {
        colleagues.at(i)->receive(msg);
      }
    }
  }

private:
  std::vector<Colleague *> colleagues;
};

void ConcreteColleague::send(std::string msg) {
  std::cout << "Message '"<< msg << "' sent by Colleague " << id << std::endl;
  mediator->distribute(this, msg);
}


int main()
{
  Mediator *mediator = new ConcreteMediator;

  Colleague *c1 = new ConcreteColleague(mediator, 1);
  Colleague *c2 = new ConcreteColleague(mediator, 2);
  Colleague *c3 = new ConcreteColleague(mediator, 3);

  mediator->add(c1);
  mediator->add(c2);
  mediator->add(c3);

  c1->send("Hi!");
  c3->send("Hello!");

  delete mediator;
  return 0;
}