设计模式学习(三)抽象工厂

意图:

提供一个创建一系列相关或相互依赖对象的接口，而无需指定它们具体的类

适用性：

一个系统要独立于它的产品的创建，组合和表示时

一个产品要由多个产品系列中的一个来配置时

当你要强调一系列相关的产品对象的设计以便进行联合使用时

当你提供一个产品类库，而只想显示它们的接口而不是实现时

代码示例：

#include "stdafx.h"#include <iostream>#include <vector>using namespace std;enum Direction{North, South, East, West};class MapSite{public:MapSite(){}virtual ~MapSite(){}virtual void Enter() = 0;};//Roomclass Room:public MapSite{public:Room(int);void SetSite(Direction,MapSite*);MapSite *GetSite(Direction) const;virtual void Enter();int GetRoomNum() const;protected:MapSite *mSite[4]; int mRoomNumber;};Room::Room(int number):mRoomNumber(number){mSite[0] = 0;//northmSite[1] = 0;//southmSite[2] = 0;//eastmSite[3] = 0;//westcout<<"Constructor Room :"<<mRoomNumber<<endl;}void Room::Enter(){}void Room::SetSite(Direction d, MapSite *map){switch(d){case North:mSite[0] = map;break;case South:mSite[1] = map;break;case East:mSite[2] = map;break;case West:mSite[3] = map;break;default:break;}}MapSite* Room::GetSite(Direction d) const{switch(d){case North:return mSite[0];case South:return mSite[1];case East:return mSite[2];case West:return mSite[3];default:return 0;}}int Room::GetRoomNum() const{return mRoomNumber;}//EnchantedRoomclass EnchantedRoom: public Room{public:EnchantedRoom(int n);void Enter();};EnchantedRoom::EnchantedRoom(int n):Room(n){cout<<"Constructor EnchantedRoom :"<<mRoomNumber<<endl;}void EnchantedRoom::Enter(){}//RoomWithABombclass RoomWithABomb: public Room{public:RoomWithABomb(int n);void Enter();};RoomWithABomb::RoomWithABomb(int n):Room(n){cout<<"Constructor RoomWithABomb :"<<mRoomNumber<<endl;}void RoomWithABomb::Enter(){;}//Wallclass Wall:public MapSite{public:Wall();void Enter();};Wall::Wall(){cout<<"Constructor a Wall"<<endl;}void Wall::Enter(){}//BombedWallclass BombedWall: public Wall{public:BombedWall();void Enter();};BombedWall::BombedWall():Wall(){cout<<"Constructor a BombedWall"<<endl;}void BombedWall::Enter(){}//doorclass Door:public MapSite{public:Door(Room* =0, Room* =0);void Enter();Room* OtherSideFrom(Room*);private:Room *mRoom1;Room *mRoom2;bool mIsOpen;};Door::Door(Room *room1, Room *room2):mRoom1(room1),mRoom2(room2),mIsOpen(false){cout<<"Constructor a Door"<<endl;}void Door::Enter(){}Room* Door::OtherSideFrom(Room *room){return 0;}//DoorNeedingSpellclass DoorNeedingSpell: public Door{public:DoorNeedingSpell(Room* =0, Room* =0);void Enter();};DoorNeedingSpell::DoorNeedingSpell(Room *r1, Room *r2):Door(r1,r2){cout<<"Constructor DoorNeedingSpell/r/n";}void DoorNeedingSpell::Enter(){}//mazeclass Maze{public:Maze();void AddRoom(Room *);Room* RoomNo(int) const;private:vector<Room*> *mRoomVec;};Maze::Maze():mRoomVec(new vector<Room*>){}void Maze::AddRoom(Room *room){mRoomVec->push_back(room);}Room* Maze::RoomNo(int number) const{vector<Room*>::const_iterator it = mRoomVec->begin();for(; it != mRoomVec->end(); ++it){if((*it)->GetRoomNum() == number){return (*it);break;}}return 0;}class MazeFactory{public:MazeFactory(){}virtual Maze* MakeMaze(){return new Maze;}virtual Room* MakeRoom(int n){return new Room(n);}virtual Door* MakeDoor(Room* r1, Room* r2){return new Door(r1,r2);}virtual Wall* MakeWall(){return new Wall;}};class Spell;class EnchantedMazeFactory :public MazeFactory{public:EnchantedMazeFactory(){}virtual Room* MakeRoom(int n){return new EnchantedRoom(n);}virtual Door* MakeDoor(Room* r1, Room* r2){return new DoorNeedingSpell(r1,r2);}protected:Spell* CastSpell();};class BombedMazeFactory: public MazeFactory{public:BombedMazeFactory(){}virtual Room* MakeRoom(int n){return new RoomWithABomb(n);}virtual Wall* MakeWall(){return new BombedWall;}};class MazeGame{public:MazeGame(){}virtual ~MazeGame(){}Maze* CreateMaze(MazeFactory& factory);};Maze* MazeGame::CreateMaze(MazeFactory& factory){Maze *aMaze = factory.MakeMaze();Room* r1 = factory.MakeRoom(1);Room* r2 = factory.MakeRoom(2);Door *theDoor = factory.MakeDoor(r1, r2);aMaze->AddRoom(r1);aMaze->AddRoom(r2);r1->SetSite(North, factory.MakeWall());r1->SetSite(South, factory.MakeWall());r1->SetSite(East, theDoor);r1->SetSite(West, factory.MakeWall());r2->SetSite(North, factory.MakeWall());r2->SetSite(South, factory.MakeWall());r2->SetSite(East, factory.MakeWall());r2->SetSite(West, theDoor);return aMaze;}int _tmain(int argc, _TCHAR* argv[]){MazeGame game; MazeFactory factory;game.CreateMaze(factory);cout<<"/r/n";EnchantedMazeFactory enchantedFactory;game.CreateMaze(enchantedFactory);cout<<"/r/n";BombedMazeFactory bombedFactory;game.CreateMaze(bombedFactory);system("pause");return 0;}

 

MazeFactory 是一个完全由工厂方法组成的具体的类，通过生产一个子类并重新定义需要改变的操作，很容易生产一个新的MazeFactory.

创建迷宫的类MazeGame的创建迷宫的方法CreateMaze将MazeFactory作为一个参数，这样就可以很方便的指定需要创建哪一类型的房间，门和墙