设计模式：工厂方法

2009-11-26 14:16 敏捷的水阅读(414) 评论(0) 编辑收藏举报

在简单工厂模式中，将实例化对象的工作推迟到了专门负责创建对象的工厂类中，可以根据我们预知动态创建产品类。但是，一旦客户的变化超过预知我们就必须修改我们的源代码（FoodShop工厂）了。

switch (foodName)
{
    case "Sugar":
        return new Sugar();                    
    case "Bread":
        return new Bread();
    default:
        throw new ArgumentException();                    
}

如何不修改工厂呢，我们这样想，我们去食品专卖店去买，到专门卖糖果的地方买糖果，专门卖面包的地方买面包，当需要买饼干时，增加一个饼干专卖店即可，不用修改工厂

namespace DP
{
    class Client
    {
        static void Main(string[] args)
        {
            // 可以从配置文件里确定具体工厂
            // IFoodshop factory = (IFoodshop)Assembly.Load("DP").
            //                     CreateInstance("SugarShop");
            IFoodshop sugarShop = new SugarShop();
 
            IFood food = sugarShop.CreateFood();
            food.Eat();
            Console.Read();
        }
    }
 
    // 抽象产品
    public interface IFood
    {
        void Eat();
    }
 
    // 具体产品
    public class Bread : IFood
    {
 
        public void Eat()
        {
            Console.WriteLine("Bread is delicious!");
        }
    }
 
    // 具体产品
    public class Sugar : IFood
    {
 
        public void Eat()
        {
            Console.WriteLine("Sugar is delicious!");
        }
    }
 
    // 抽象工厂
    public interface IFoodshop
    {
        IFood CreateFood();
         
    }
 
    // 具体工厂
    public class SugarShop : IFoodshop
    {
        public IFood CreateFood()
        {
            return new Sugar();
        }
        
    }
 
    // 具体工厂
    public class BreadShop : IFoodshop
    {
        public IFood CreateFood()
        {
            return new Bread();
        }
 
    }
     
}