visitor_example.cpp

#include "visitor.hpp"
#include <iostream>

class OtherTypeAsteroid;
class ExplodingAsteroid;
class ApolloSpacecraft;
class OthersSpacecraft;

class SpaceShip {};
class Asteroid : public Visitor<ApolloSpacecraft, OthersSpacecraft>{};
class Alien : public Visitor<ApolloSpacecraft, OthersSpacecraft>{};

struct OthersSpacecraft : public SpaceShip, public Visitable<OthersSpacecraft, Asteroid, Alien> {};

struct ApolloSpacecraft : public SpaceShip, public Visitable<ApolloSpacecraft, Asteroid, Alien> {};
 
class ExplodingAsteroid : public Asteroid {
public:
  virtual void visit(OthersSpacecraft&) {
    std::cout << "ExplodingAsteroid hit a OthersSpacecraft" << std::endl;
  }
  virtual void visit(ApolloSpacecraft&) {
    std::cout << "ExplodingAsteroid hit an ApolloSpacecraft" << std::endl;
  }
};

class OtherTypeAsteroid : public Asteroid {
public:
  virtual void visit(OthersSpacecraft&) {
    std::cout << "OtherTypeAsteroid hit a OthersSpacecraft" << std::endl;
  }
  virtual void visit(ApolloSpacecraft&) {
    std::cout << "OtherTypeAsteroid hit an ApolloSpacecraft" << std::endl;
  }
};

struct AlienA : public Alien
{
    virtual void visit(OthersSpacecraft&) {
        std::cout << "AlienA hit a OthersSpacecraft" << std::endl;
    }
    virtual void visit(ApolloSpacecraft&) {
        std::cout << "AlienA hit an ApolloSpacecraft" << std::endl;
    }
};

struct AlienB : public Alien
{
    virtual void visit(OthersSpacecraft&) {
        std::cout << "AlienB hit a OthersSpacecraft" << std::endl;
    }
    virtual void visit(ApolloSpacecraft&) {
        std::cout << "AlienB hit an ApolloSpacecraft" << std::endl;
    }
};

int main()
{
    OthersSpacecraft theOthersSpacecraft;
    ApolloSpacecraft theApolloSpacecraft;
    
    OtherTypeAsteroid theOtherTypeAsteroid;
    ExplodingAsteroid theExplodingAsteroid;

    Asteroid& theAsteroidReference = theExplodingAsteroid;
    Visitable<Asteroid>& theSpaceShipReference_1 = theApolloSpacecraft;

    theSpaceShipReference_1.accept(theOtherTypeAsteroid);
    theSpaceShipReference_1.accept(theAsteroidReference);
    
    AlienA theAlienA;
    AlienB theAlienB;

    Alien& theAlienReference = theAlienB;
    Visitable<Alien>& theSpaceShipReference_2 = theOthersSpacecraft;

    theSpaceShipReference_2.accept(theAlienA);
    theSpaceShipReference_2.accept(theAlienReference);

    return 0;
}