design-patterns-cpp/command/Command.cpp

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

#include <iostream>

/*
 * Receiver
 * knows how to perform the operations associated 
 * with carrying out a request
 */
class Receiver {
public:
  void action() {
    std::cout << "Receiver: execute action" << std::endl;
  }
  // ...
};

/*
 * Command
 * declares an interface for all commands
 */
class Command {
public:
  virtual ~Command() {}
  virtual void execute() = 0;
  // ...
  
protected:
  Command() {}
};

/*
 * Concrete Command
 * implements execute by invoking the corresponding 
 * operation(s) on Receiver 
 */
class ConcreteCommand : public Command {
public:
  ConcreteCommand(Receiver *r)
    : receiver(r) {}

  ~ConcreteCommand() {
    if (receiver) {
      delete receiver;
    }
  }

  void execute() {
    receiver->action();
  }
  // ...
  
private:
  Receiver *receiver;
  // ...
};

/*
 * Invoker
 * asks the command to carry out the request
 */
class Invoker {
public:
  void set(Command *c) {
    command = c;
  }

  void confirm() {
    if (command) {
      command->execute();
    }
  }
  // ...

private:
  Command *command;
  // ...
};


int main()
{
  Receiver receiver = Receiver();
  ConcreteCommand command = ConcreteCommand(&receiver);

  Invoker invoker = Invoker();
  invoker.set(&command);
  invoker.confirm();

  return 0;
}