c#设计模式之策略者模式(Strategy Pattern)

场景出发

假设存在如下游戏场景:

1:角色可以装备木剑,铁剑,魔剑3种装备,分别对怪物造成20HP,50HP,100HP伤害(未佩戴装备则无法攻击);

2角色可以向怪物攻击,一次攻击后损失角色所佩戴装备的HP伤害,当HP损失完毕后,怪物死亡;

不假思索地我会写出如下的代码:

   class Monster

     {

         public string Name { get; set; }

         public int HP { get; set; }

         /// <summary>

         /// 怪物被攻击后提示

         /// </summary>

         /// <param name="loss">武器造成的HP伤害损失</param>

         public void Warn(int loss)

         {

             if (HP <= )

             {

                 Console.WriteLine($"怪物{Name}已经死亡");

                 return;

             }

             HP -= loss;

             Console.WriteLine($"怪物{Name}受到{loss}HP伤害");

             if (HP <= )

             {

                 Console.WriteLine($"怪物{Name}被打死了");

             }

         }

     }

   class Role

     {

         public string Name { get; set; }

         public string Weapon { get; set; }

         /// <summary>

         /// 武器攻击

         /// </summary>

         /// <param name="monster">攻击的怪物对象</param>

         public void Attack(Monster monster)

         {

             if (Weapon == "WoodenSword")

             {

                 Console.WriteLine($"{Name}用木剑攻击了{monster.Name}");

                 monster.Warn();

             }

             else if (Weapon == "IronSword")

             {

                 Console.WriteLine($"{Name}用铁剑攻击了{monster.Name}");

                 monster.Warn();

             }

             else if (Weapon == "MagicSword")

             {

                 Console.WriteLine($"{Name}用魔剑攻击了{monster.Name}");

                 monster.Warn();

             }

             else

             {

                 Console.WriteLine($"{Name}没有武器,无法攻击");

             }

         }

     }

     class Program

     {

         static void Main(string[] args)

         {

             var monster = new Monster()

             {

                 Name = "沼泽首领",

                 HP =

             };

             var role = new Role()

             {

                 Name = "狂战士",

                 Weapon="IronSword"

             };

             role.Attack(monster);

             role.Weapon = "WoodenSword";

             role.Attack(monster);

             role.Weapon = "MagicSword";

             role.Attack(monster);

             Console.ReadKey();

         }

     }

相信不止我一个人会这样写,因为它能快速的"完美的"实现上述功能

回过头来再仔细观察这段代码,就感觉像在看一段"直肠子",所有的逻辑算法都集中到了一个管道上,只要有需求或逻辑上的的变化,那么就得直接去修改业务类

策略者模式

其实很多时候我们都会遇到上述这种情况,一个业务类中存在这种逻辑,多个if...else来判断选择逻辑策略,这个时候如果直接写入业务类,严重违背了OCP原则(开放关闭原则:对扩展开放,对修改关闭)

将上述的场景通过策略者模式来解决,代码如下

    /// <summary>

     /// 武器攻击的抽象

     /// </summary>

     public interface IWeaponStrategy

     {

         void WeaponAttack(Monster monster);

     }

     public class WoodenSwordStrategy : IWeaponStrategy

     {

         public void WeaponAttack(Monster monster)

         {

             Console.WriteLine("木剑攻击");

             monster.Warn();

         }

     }

     public class IronSwordStrategy : IWeaponStrategy

     {

         public void WeaponAttack(Monster monster)

         {

             Console.WriteLine("铁剑攻击");

             monster.Warn();

         }

     }

     public class MagicSwordStrategy : IWeaponStrategy

     {

         public void WeaponAttack(Monster monster)

         {

             Console.WriteLine("魔剑攻击");

             monster.Warn();

         }

     }

    public class Monster

     {

         public string Name { get; set; }

         public int HP { get; set; }

         /// <summary>

         /// 怪物被攻击后提示

         /// </summary>

         /// <param name="loss">武器造成的HP伤害损失</param>

         public void Warn(int loss)

         {

             if (HP <= )

             {

                 Console.WriteLine($"怪物{Name}已经死亡");

                 return;

             }

             HP -= loss;

             Console.WriteLine($"怪物{Name}受到{loss}HP伤害");

             if (HP <= )

             {

                 Console.WriteLine($"怪物{Name}被打死了");

             }

         }

     }

     class Role

     {

         public string Name { get; set; }

         public IWeaponStrategy Weapon { get; set; }

         public void Attack(Monster monster)

         {

             Weapon.WeaponAttack(monster);

         }

     }

     class Program

     {

         static void Main(string[] args)

         {

             var monster = new Monster()

             {

                 Name = "沼泽首领",

                 HP =

             };

             var role = new Role()

             {

                 Name = "狂战士",

                 Weapon=new IronSwordStrategy()

             };

             role.Attack(monster);

             role.Weapon = new WoodenSwordStrategy();

             role.Attack(monster);

             role.Weapon = new MagicSwordStrategy();

             role.Attack(monster);

             Console.ReadLine();

         }

     }