【C#】Behavioral Patterns Chain of Responsibility Mode

The Chain of Responsibility design pattern avoids coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. This pattern chains the receiving objects and passes the request along the chain until an object handles it.

责任链设计模式通过为多个对象提供处理请求的机会，避免将请求的发送者与其接收者耦合~ 此模式链接接收对象并沿链传递请求，直到对象处理它~ 有点像是自制版的Switch Case~

学习目标: 责任链模式的概念及实务

学习难度: ☆☆☆

using System;

namespace ConsoleApp1
{
    public abstract class Handler
    {
        protected Handler NextHandler;

        public void SetNextHandler(Handler nexthandler)
        {
            this.NextHandler = nexthandler;
        }

        public abstract void HandleRequest(string country);
    }

    public class ConcreteHandler1 : Handler
    {
        public override void HandleRequest(string country)
        {
            if (country == "Russia")
            {
                Console.WriteLine("Russia is Europe country");
            }
            else if (country == "Germany")
            {
                Console.WriteLine("Germany is Europe country");
            }
            else if (NextHandler != null)
            {
                NextHandler.HandleRequest(country);
            }
        }
    }

    public class ConcreteHandler2 : Handler
    {
        public override void HandleRequest(string country)
        {
            if (country == "Taiwan")
            {
                Console.WriteLine("Taiwan is Asia country");
            }
            else if (country == "China")
            {
                Console.WriteLine("China is Asia country");
            }
            else if (NextHandler != null)
            {
                NextHandler.HandleRequest(country);
            }
            else
            {
                Console.WriteLine("Not found..");
            }
        }
    }

    public class MainProgram
    {
        public static void Main(string[] args)
        {
            Handler h1 = new ConcreteHandler1();

            Handler h2 = new ConcreteHandler2();

            h1.SetNextHandler(h2); //有点像指向的概念...

            string[] countries = { "Taiwan", "Russia", "China", "Russia" };

            foreach (string country in countries)
            {
                h1.HandleRequest(country); //要求判断...
            }
        }
    }
}

参考资料:

https://www.dofactory.com/net/chain-of-responsibility-design-pattern