理解设计模式[策略模式]

1.前言
设计模式一般分为三大类

策略模式属于行为型模式,(即影响软件运行的一种因素)
主要的目的是抽取一些可以被替换的算法部分,(便于添加新的内容,而不重新再去修改原來的方法[開閉原則])
就像导航里面会显示步行,骑行,公交等等出行方式所估计的时间一样,这就是一种策略模式的体现

它的类图也很简单,
[这里放一张类图]

如果按简单的角色分类,则可以分为

1. 抽象策略接口
2. 具体策略类
3. 客户端(策略的使用者)

策略模式的Java代码实现

public interface Strategy {
	
	
	double CountTravelTime(int distance);

}

public class WalkStrategy implements Strategy {
	
	//步行的速度,單位為米/分
    private int WalkSpeed = 80;

    @Override
	public double CountTravelTime(int distance) {	
		return distance/WalkSpeed;
	}
      
}

public class RideStrategy implements Strategy {
	
	//騎行速度,單位米/分
	private int RideSpeed = 300;

	@Override
	public double CountTravelTime(int distance) {
		return distance/RideSpeed;
	}
	
}

public class DriveStrategy implements Strategy{

	//乘車速度,單位米/分
	private int DriveSpeed = 800;
	
	@Override
	public double CountTravelTime(int distance) {
		return distance/DriveSpeed;
	}

}

public class NavSystem {
	
	private int distance;
	
	//在客户端中引用一个策略模式的实例,用于设置策略
	private Strategy strategy;
	
	public NavSystem(Strategy strategy) {
		this.strategy = strategy;
	}
	public NavSystem() {
	}

	public Strategy getStrategy() {
		return strategy;
	}

	public void setStrategy(Strategy strategy) {
		this.strategy = strategy;
	}

	public void setdistance(int distance) {
		this.distance = distance;
	}
	
	//根据不同的策略进行不同的计算,并提示一些信息
	public void GOTraveling() {
		if(strategy instanceof WalkStrategy) {
			System.out.println("你選擇的是步行策略,你將花費"+strategy.CountTravelTime(distance)+"m的時間");
			if(strategy.CountTravelTime(distance)>30) {
				System.out.println("步行時間過長");
			}
		}
		else if(strategy instanceof RideStrategy) {
			System.out.println("你選擇的是騎行策略,你將花費"+strategy.CountTravelTime(distance)+"m的時間");
			if(strategy.CountTravelTime(distance)>30) {
				System.out.println("騎行時間過長");
			}
		}
		else if(strategy instanceof DriveStrategy) {
			System.out.println("你選擇的是開車策略,你將花費"+strategy.CountTravelTime(distance)+"m的時間");	
		}
	}
	
}

测试的主函数

public class MainTest {
	public static void main(String[] args) {
		NavSystem system = new NavSystem();
		RideStrategy ride = new RideStrategy();
		system.setStrategy(ride);
		system.setdistance(12333);
		system.GOTraveling();
	}
}

结果

你選擇的是騎行策略,你將花費41.0m的時間
騎行時間過長

C#代码也是同理

/// 

/// 策略模式的C#代碼實現
/// 
namespace EFCoreDemo2.Models
{
    public class Enemy
    {
        public int attack { get; set; }

        public int defend { get; set; }

        public Enemy(int attack, int defend, int hP)
        {
            this.attack = attack;
            this.defend = defend;
            HP = hP;
        }
        public Enemy()
        {
        }
        public int HP { get; set; }
    }

    public class Gamer
    {
        public int attack { get; set; }

        public int defend { get; set; }

        public Gamer(int attack, int defend, int hP)
        {
            this.attack = attack;
            this.defend = defend;
            HP = hP;
        }

        public Gamer()
        {
        }

        public int HP { get; set; }
    }

    interface Strategy
    {
        void setGamer(Gamer gamer);
        bool BattleInGame(Enemy enemy);
    }


    public class AttackStrategy : Strategy
    {
        public Gamer gamer { get; set; }

        public bool BattleInGame(Enemy enemy)
        {
            gamer.attack += 20;
            gamer.defend -= 20;
            if (enemy.defend >= gamer.attack)
            {
                return false;
            }
            else
            {
                int dis = gamer.attack - enemy.defend;
                int dis2 = enemy.attack - gamer.defend;
                if ((enemy.HP / dis) < (gamer.HP / dis2))
                    return true;
                else
                    return false;
            }
           
        }

        public void setGamer(Gamer gamer)
        {
            this.gamer = gamer;
        }
    }

    public class DefendStrategy : Strategy
    {
        public Gamer gamer { get; set; }

        public bool BattleInGame(Enemy enemy)
        {
            gamer.defend += 20;
            gamer.attack -= 20;
            if (gamer.defend >= enemy.attack)
            {
                return true;
            }
            else
            {
                int dis = gamer.attack - enemy.defend;
                int dis2 = enemy.attack - gamer.defend;
                if ((enemy.HP / dis) < (gamer.HP / dis2))
                    return true;
                else
                    return false;
            }
        }

        public void setGamer(Gamer gamer)
        {
            this.gamer = gamer;
        }
    }

    public class StandStrategy : Strategy
    {
        public Gamer gamer { get; set; }
        
        public bool BattleInGame(Enemy enemy)
        {
            gamer.attack += 10;
            gamer.defend -= 20;
            int dis = gamer.attack - enemy.defend;
            int dis2 = enemy.attack - gamer.defend;
            if ((enemy.HP / dis) < (gamer.HP / dis2))
                return true;
            else
                return false;
        }

        public void setGamer(Gamer gamer)
        {
            this.gamer = gamer;
        }
    }

    

}

測試:

    class Program
    {
        public class Game
        {
            private Strategy strategy;

            public void setStrategy(Strategy strategy)
            {
                this.strategy = strategy;
            }

            public void Battle(Enemy enemy)
            {
                if (strategy.BattleInGame(enemy))
                {
                    Console.WriteLine("你擊敗了敵人");
                }
                else
                {
                    Console.WriteLine("你失敗了");
                }
            }
        }
            

        static void Main(string[] args)
        {
            Strategy strategy = new AttackStrategy();
            strategy.setGamer(new Gamer(100, 80, 100));

            Game game = new Game();
            game.setStrategy(strategy);

            game.Battle(new Enemy(120, 30, 80));

        }
    }

結果:

你擊敗了敵人