Design Pattern – Factory Pattern (二)

Factory Pattern

現在假設我的飲料店有很多家了, 但台北與高雄不同的店, 需要的原料會不同

所以若有個原料產生的工廠呢?

public interface SourceFactory{
    public Sugar createSugar();
    public Ice createIce();
}
public class TaipeiSourceFactory implements SourceFactory{
    public Sugar createSugar(){
        return new Sugar();
    }
    public Ice createIce(){
        return new Ice();
    }
}
public class KaoshungSourceFactory implements SourceFactory{
    //自訂高雄的工廠要怎麼生產原料 xxx
}

public abstract class Beverage{
    Sugar sugar;
    Ice ice;
    abstract void prepare();
    public void box(){
//把飲料裝箱
   }
}
public class MikeTeaBeverage extends Beverage{ //做奶茶
    TaipeiSourceFactory taipeiSourceFactory ;  
    public MikeTeaBeverage(TaipeiSourceFactory  taipeiSourceFactory ){
          this.taipeiSourceFactory = taipeiSourceFactory ;  
    }
    void prepare(){  
        Sugar sugar = taipeiSourceFactory.createSugar();
        Ice ice = taipeiSourceFactory.createIce();  
    }
}  
public class BlackTeaBeverage extends Beverage{
    //相同 xxx
}

我覺上面的寫法, 跟使用utils的想法類似, 把會重複利用的拉出來

最後, 上一篇的BeverageShop, 我們來extends它, 就可以很容易的擴充了

public class CocoBeverageShop extends BeverageShop{
    public Beverage createBeverage(String type){
        Beverage beverage;
        SourceFactory factory = new TaipeiSourceFactory(); //我coco的店要用台北的原料
        if(type.equals(「紅茶")){
            ...
        }else if(type.equals(「奶茶")){
            beverage = new MikeTeaBeverage(factory);
        }
        return beverage;
    }
}

要依賴抽象, 不要依賴實作的類 --> 不是我講的

會變動的東西, 就把它變成抽象,再去實作, 這樣物件之間的關係就可以分開