工厂方法模式的优点(Advantage of factory method pattern)

 来自维基 ， 
 
 Factory Method设计模式解决了以下问题： 
 
 
 
 如何创建对象以便子类可以重新定义要实例化的类？ 
 
 
 类如何将实例化推迟到子类？ 
 
 
 例如， MazeGame为类似MagicMazeGame子类提供实例化功能。 
 
  
 
 哪里， 
 
public abstract class MazeGame {
    private final List<Room> rooms = new ArrayList<>();

    public MazeGame() {
        Room room1 = makeRoom();
        Room room2 = makeRoom();
        room1.connect(room2);
        rooms.add(room1);
        rooms.add(room2);
    }

    abstract protected Room makeRoom();
}
 
 
 阅读答案 。 
 
 当然，这是一种创造性的模式，因此设计应该围绕简化类的实例化。 
 
 
 我的问题是， 
 
 工厂方法模式的优点是什么，引入提供模板方法的MagicGame类（ public MazeGame(){..} ）并将实例化推迟到子类MagicMazeGame或OrdinaryMazeGame ？ 
 
 将实例化推迟到子类只是为了抽象类MagicMazeGame的下面的复杂性， 
 
        Room room1 = MagicMazeGame();
        Room room2 = MagicMazeGame();
        room1.connect(room2);
        rooms.add(room1);
        rooms.add(room2);
 
 并在每个类MagicMazeGame或类OrdinaryMazeGame提供统一的创建逻辑，如下所示， 
 
public class MagicMazeGame extends MazeGame {
    public MagicMazeGame() {
        super();
    } 
    @Override
    protected Room makeRoom() {
        return new MagicRoom(); 
    }
}

From wiki,
 
The Factory Method design pattern solves problems like: 
 
 
 
How can an object be created so that subclasses can redefine which class to instantiate?
 
 
How can a class defer instantiation to subclasses?
 
 
For example, MazeGame provides the instantiation capability to subclass like MagicMazeGame.
 
 
where,
 
public abstract class MazeGame {
    private final List<Room> rooms = new ArrayList<>();

    public MazeGame() {
        Room room1 = makeRoom();
        Room room2 = makeRoom();
        room1.connect(room2);
        rooms.add(room1);
        rooms.add(room2);
    }

    abstract protected Room makeRoom();
}
 
 
Read answer.
 
Of course, this is a creational pattern, so design should be around simplifying instantiation of a class.
 
 
My question is, 
 
What is the advantage of factory method pattern, introducing MagicGame class that provides a template method(public MazeGame(){..}) and defer instantiation to subclass MagicMazeGame or OrdinaryMazeGame? 
 
Is deferring instantiation to subclass for only abstracting the below intricacies in a class like MagicMazeGame,
 
        Room room1 = MagicMazeGame();
        Room room2 = MagicMazeGame();
        room1.connect(room2);
        rooms.add(room1);
        rooms.add(room2);
 
and provide a uniform creation logic in every class MagicMazeGame or class OrdinaryMazeGame, as shown below,
 
public class MagicMazeGame extends MazeGame {
    public MagicMazeGame() {
        super();
    } 
    @Override
    protected Room makeRoom() {
        return new MagicRoom(); 
    }
}

原文：https://stackoverflow.com/questions/47938020