iamgsi

#include <iostream>
#include <string>
using namespace std;

//////////////////////////////////////////////////////////////////////////
class GameLevel
{
public:
 static GameLevel* CreateInstance() { return 0; }
 virtual void SimpleAttack() = 0;

protected:
 GameLevel() {}
};

//////////////////////////////////////////////////////////////////////////
class Gamelevel0 : public GameLevel
{
public:
 static GameLevel* CreateInstance()
 {
  if(pInstance == 0) pInstance = new Gamelevel0();
  return pInstance;
 }

 void SimpleAttack() { cout << "Level0 Simple Attack" << endl; }

protected:
 Gamelevel0() {}

private:
 static Gamelevel0 *pInstance;
};
Gamelevel0* Gamelevel0::pInstance = 0;

//////////////////////////////////////////////////////////////////////////
class Gamelevel1 : public GameLevel
{
public:
 static GameLevel* CreateInstance()
 {
  if(pInstance == 0) pInstance = new Gamelevel1();
  return pInstance;
 }

 void SimpleAttack() { cout << "Level1 Simple Attack" << endl; }

protected:
 Gamelevel1() {}

private:
 static Gamelevel1 *pInstance;
};
Gamelevel1* Gamelevel1::pInstance = 0;

//////////////////////////////////////////////////////////////////////////

class GamePlayer
{
public:
 GamePlayer()
 {
  pGameLevel = Gamelevel0::CreateInstance();
 }

 void UpgradeLevel(GameLevel* pLevel)
 {
  pGameLevel = pLevel;
 }

 void SimpleAttack()
 {
  pGameLevel->SimpleAttack();
 }

private:
 GameLevel* pGameLevel;
};

//////////////////////////////////////////////////////////////////////////
int _tmain(int argc, _TCHAR* argv[])
{
 GamePlayer user1;

 user1.SimpleAttack();
 cout << "------------------------------------------" << endl;

 GameLevel* pGameLevel1 = Gamelevel1::CreateInstance();
 user1.UpgradeLevel(pGameLevel1);

 user1.SimpleAttack();

 return 0;
}