简单工厂模式

情景：有一个怪兽，HP是100，现在勇士有可以使用武器将其打败，有三种武器，木剑每次打击20血，铁剑每次50血，金刚剑每次100血，如果想要使用简单工厂方式，怎么设计？

一.啥是简单工厂？

通过专门定义一个类来负责创建其他类的实例，被创建的实例通常都具有共同的父类。

结构大概如下图：

画出场景的类图

解释：

1.Sword是一个基类，通过其中有一个字段保存怪物的血量，还有一个虚方法是打击怪物的方法

2.有三个具体的武器的类，分别对应木剑、铁剑、金刚剑，实现了各种对怪物打击的逻辑

3.CreateSwordFactory类，是具体实例化武器的类，通过客户端的调用，可以传入想要创建的武器。

4.Program就是客户端

 

二.具体的代码

1.Sword.cs类

namespace SimpleFactory
{
        public class Sword
        {
                protected int monsterLife = 100;
                public virtual void beat()
                {
                        
                }
        }
}

2.WoodSword.cs

namespace SimpleFactory
{
        public class WoodSword : Sword
        {
                public override void beat()
                {
                        while (monsterLife > 0)
                        {
                                base.monsterLife -= 20;
                                Console.WriteLine("The Monster is already alive！");
                        }
                        Console.WriteLine("Excellent!The Monster is dead!"); 
                }
        }
}

 3.IronSword.cs

namespace SimpleFactory
{
        public class IronSword:Sword
        {
                public override void beat()
                {
                        while (monsterLife > 0)
                        {
                                base.monsterLife -= 50;
                                Console.WriteLine("The Monster is already alive！");
                        }
                        Console.WriteLine("Excellent!The Monster is dead!"); 
                }
        }
}

4.DiamondSword.cs

namespace SimpleFactory
{
      public class DiamondSword:Sword
        {
              public override void beat()
                {
                        while (monsterLife > 0)
                        {
                                base.monsterLife -= 100;
                                Console.WriteLine("The Monster is already alive！");
                        }
                        Console.WriteLine("Excellent!The Monster is dead!"); 
                }
        }
}

5.CreateSwordFactory.cs

namespace SimpleFactory
{
        public class CreateSwordFactory
        {
                public static Sword CreateSword(string sword)
                {
                        Sword s = null;
                        switch (sword)
                        { 
                                case "WoodSword":
                                          s = new WoodSword();
                                        break;
                                case "IronSword":
                                          s = new IronSword();
                                        break;
                                case "DiamondSword":
                                          s = new DiamondSword();
                                        break;
                                default:
                                        break;
                        }
                        return s;
                }
        }
}

6.Program.cs

namespace SimpleFactory
{
        class Program
        {
                static void Main(string[] args)
                {
                        Sword s = CreateSwordFactory.CreateSword("WoodSword");
                        s.beat();
                        Console.WriteLine("----------------------");
                        s=CreateSwordFactory.CreateSword("IronSword");
                        s.beat();
                        Console.WriteLine("----------------------");
                        s = CreateSwordFactory.CreateSword("DiamondSword");
                        s.beat();
                }
        }
}

 

三.运行效果和总结

效果：

总结：

简单工厂模式的优缺点： 

       优点：如下图所示，这时候我们添加一个其他的剑，那么我不需要去修改我红色区域的东西，仅仅修改CreateSwordFactory.cs这个类就行，然后这个类根据客户端给出的具体产生什么剑再去实例化就可以了。不需要了解具体每一个剑是怎么被创建的。

缺点：以为过多的依赖于工厂类，简单工厂模式违背了“开放封闭原则”，就是违背了“系统对扩展开放，对修改关闭”的原则，因为当我新增加一个剑的时候必须修改工厂类，相应的工厂类就需要重新编译一遍。