{C#}设计模式辨析.责任链

背景

• 按定义好的职权流程，下拨任务。

示例

using static System.Console;

namespace DesignPattern_ChainOfResponsibility
{
    // 接口，确保层级间互换
    public interface IHandler
    {
        IHandler SetNext(IHandler next); // 设置下级组成责任链，流畅格式(类似lambda)
        void Handle(decimal cost); // 按职权处理
    }

    // 抽象类，包含公共(默认)代码
    public abstract class Handler : IHandler
    {
        private IHandler next;
        private readonly decimal limit;

        public Handler(decimal limit)
        {
            this.limit = limit;
        }

        public virtual void Handle(decimal cost)
        {
            // 最后一人 或职权范围内
            if (next == null || cost >= limit)
            {
                WriteLine($"Cost of {cost}RMB is handled by {GetType().Name}.");
                return;
            }

            next.Handle(cost);
        }

        public IHandler SetNext(IHandler next)
        {
            this.next = next;

            return next;
        }
    }

    // 总裁类，责任链入口
    public class President : Handler
    {
        public President(decimal limit) : base(limit) { }
    }

    // 经理类
    public class Manager : Handler
    {
        public Manager(decimal limit) : base(limit) { }
    }

    // 文员类
    public class Clerk : Handler
    {
        public Clerk(decimal limit) : base(limit) { }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var president = new President(1000_0);
            president
                .SetNext(new Manager(1000))
                .SetNext(new Clerk(-1));

            president.Handle(2000_0);
            president.Handle(2000);
            president.Handle(200);

            ReadKey();
        }
    }
}