抽象工廠(Abstract Factory)模式看起來和前面看到的工廠方法很相似，只是它使用若干工廠方法(Factory Method）模式。每個工廠方法模式創(chuàng)建一個不同類型的對象。當(dāng)創(chuàng)建一個工廠對象時，要決定將如何使用由那個工廠創(chuàng)建的所有對象。示例代碼如下（假設(shè)要創(chuàng)建一個通用的游戲環(huán)境，并且希望它能支持不同類型的游戲）：
#include<iostream>
using namespace std;
class Obstacle
{
public:
virtual void action()=0;
};
class Player
{
public:
virtual void interactWith(Obstacle*)=0;
};
class Kitty: public Player
{
virtual void interactWith(Obstacle *ob)
{
cout<<"Kitty has encountered a";
ob->action();
}
};
class KungFuGuy: public Player
{
virtual void interactWith(Obstacle* ob)
{
cout<<"KungFuGuy now battles against a";
ob->action();
}
};
class Puzzle: public Obstacle
{
public:
void action(){cout<<"Puzzle"<<endl;}
};
class NastyWeapon: public Obstacle
{
public:
void action(){cout<<"NastyWeapon"<<endl;}
};
//the abstract factory
class GameElementFactory
{
public:
virtual Player* makePlayer()=0;
virtual Obstacle* makeObstacle()=0;
};
//concreate factories
class KittiesAndPuzzles:public GameElementFactory
{
public:
virtual Player* makePlayer(){return new Kitty;}
virtual Obstacle * makeObstacle(){return new Puzzle;}
};
class KillAndDismember:public GameElementFactory
{
public:
virtual Player* makePlayer(){return new KungFuGuy;}
virtual Obstacle *makeObstacle(){return new NastyWeapon;}
};
class GameEnvironment
{
GameElementFactory* gef;
Player* p;
Obstacle *ob;
public:
GameEnvironment(GameElementFactory * factory)
:gef(factory),p(factory->makePlayer()),ob(factory->makeObstacle()){}
void play(){p->interactWith(ob);}
~GameEnvironment()
{
delete p;
delete ob;
delete gef;
}
};
int main()
{
GameEnvironment
g1(new KittiesAndPuzzles),
g2(new KillAndDismember);
g1.play();
g2.play();
}
在此環(huán)境中，Player對象與Obstacle 對象交互，但是Player和Obstacle類型依賴于具體的游戲。可以選擇特定的GameElementFactory來決定游戲的類型，然后GameEnvironment控制游戲的設(shè)置和進(jìn)行。在本例中，游戲的設(shè)置和進(jìn)行很簡單，但是那些動作在很大程度上決定了游戲的結(jié)果。