笔记：Gof设计模式--Abstract Factory

1、意图

    Provide an interface for creating families of related or dependent objects without specifying their concrete classes. 

 

2、适应性

Use the Abstract Factory pattern when     ••

    • a system should be independent of how its products are created, composed, and represented.

    • a system should be configured with one of multiple families of products.

    • a family of related product objects is designed to be used together, and you need to enforce this constraint.

    •you want to provide a class library of products, and you want to reveal just their interfaces, not their implementations.•

 

3、结构

                  

 

4、示例代码 

class MazeFactory {     public:         MazeFactory();              virtual Maze* MakeMaze() const             { return new Maze; }         virtual Wall* MakeWall() const             { return new Wall; }         virtual Room* MakeRoom(int n) const             { return new Room(n); }         virtual Door* MakeDoor(Room* r1, Room* r2) const             { return new Door(r1, r2); }     }; 

 class EnchantedMazeFactory : public MazeFactory {     public:         EnchantedMazeFactory();              virtual Room* MakeRoom(int n)  const             { return new EnchantedRoom(n, CastSpell()); }              virtual Door* MakeDoor(Room* r1, Room* r2)  const             { return new DoorNeedingSpell(r1, r2); }          protected:         Spell* CastSpell() const;     }; 

   Maze* MazeGame::CreateMaze (MazeFactory& factory) {         Maze* aMaze = factory.MakeMaze();         Room* r1 = factory.MakeRoom(1);         Room* r2 = factory.MakeRoom(2);         Door* aDoor = factory.MakeDoor(r1, r2);              aMaze->AddRoom(r1);         aMaze->AddRoom(r2);              r1->SetSide(North, factory.MakeWall());         r1->SetSide(East, aDoor);         r1->SetSide(South, factory.MakeWall());         r1->SetSide(West, factory.MakeWall());              r2->SetSide(North, factory.MakeWall());         r2->SetSide(East, factory.MakeWall());         r2->SetSide(South, factory.MakeWall());         r2->SetSide(West, aDoor);              return aMaze;     }