command.cpp

#include <iostream>
 
using namespace std;

class Command {
  public:
    virtual void execute() = 0;
};
 
class Light {
  public:
    void on() {
      cout << "The light is on\n";
    }
    void off() {
      cout << "The light is off\n";
    }
}; 

// Command for turning on the light
class LightOnCommand : public Command {
  public:
    LightOnCommand(Light *light) : mLight(light) {}
    void execute(){
      mLight->on();
    }
    private:
      Light *mLight;
};
 
// Command for turning off the light
class LightOffCommand : public Command {
  public:
    LightOffCommand(Light *light) : mLight(light) {}
    void execute(){
      mLight->off();
    }
  private:
    Light *mLight;
};

// Invoker 
// Stores the ConcreteCommand object 
class RemoteControl {
  public:
    void setCommand(Command *cmd) {
      mCmd = cmd;
    }
    void buttonPressed() {
      mCmd->execute();
    } 
  private:
    Command *mCmd;
};
 
// The client
int main()  {
  // Receiver 
  Light *light = new Light;

  // concrete Command objects 
  LightOnCommand *lightOn = new LightOnCommand(light);
  LightOffCommand *lightOff = new LightOffCommand(light);

  // invoker objects
  RemoteControl *control = new RemoteControl;

  // execute
  control->setCommand(lightOn);
  control->buttonPressed();
  control->setCommand(lightOff);
  control->buttonPressed();

  delete light, lightOn, lightOff, control;

  return 0;
}