21.责任链模式

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication4
{
    class Program
    {
        //责任链模式指的是——某个请求需要多个对象进行处理，
        //从而避免请求的发送者和接收之间的耦合关系。
        //将这些对象连成一条链子，并沿着这条链子传递该请求，直到有对象处理它为止。
        static void Main(string[] args)
        {
            PurchaseRequest requestTelphone = new PurchaseRequest(4000.0, "电话");
            PurchaseRequest requestSoftware = new PurchaseRequest(10000.0, "软件");
            PurchaseRequest requestComputers = new PurchaseRequest(40000.0, "电脑");
            PurchaseRequest requestCar = new PurchaseRequest(140000.0, "汽车");

            Approver manager = new Manager("经理");
            Approver Vp = new VicePresident("副总");
            Approver Pre = new President("老板");

            // 设置责任链
            manager.NextApprover = Vp;
            Vp.NextApprover = Pre;

            // 处理请求
            manager.ProcessRequest(requestTelphone);
            manager.ProcessRequest(requestSoftware);
            manager.ProcessRequest(requestComputers);
            manager.ProcessRequest(requestCar);
            Console.ReadLine();
        }

        // 采购请求
        public class PurchaseRequest
        {
            // 金额
            public double Amount { get; set; }
            // 产品名字
            public string ProductName { get; set; }
            public PurchaseRequest(double amount, string productName)
            {
                Amount = amount;
                ProductName = productName;
            }
        }


        // 审批人,Handler
        public abstract class Approver
        {
            public Approver NextApprover { get; set; }
            public string Name { get; set; }
            public Approver(string name)
            {
                this.Name = name;
            }
            public abstract void ProcessRequest(PurchaseRequest request);
        }


        // ConcreteHandler,经理
        public class Manager : Approver
        {
            public Manager(string name)
                : base(name)
            {}

            //少于10000块，可以决定
            public override void ProcessRequest(PurchaseRequest request)
            {
                if (request.Amount < 10000.0)
                {
                    Console.WriteLine("{0}：{1}少于10000块，{2}可以批准！", request.ProductName, request.Amount,Name);
                }
                else if (NextApprover != null)
                {
                    NextApprover.ProcessRequest(request);
                }
            }
        }


        // ConcreteHandler,副总
        public class VicePresident : Approver
        {
            public VicePresident(string name)
                : base(name)
            {}

            //少于25000块，可以决定
            public override void ProcessRequest(PurchaseRequest request)
            {
                if (request.Amount < 25000.0)
                {
                    Console.WriteLine("{0}：{1}少于10000块，{2}可以批准！", request.ProductName, request.Amount, Name);
                }
                else if (NextApprover != null)
                {
                    NextApprover.ProcessRequest(request);
                }
            }
        }


        // ConcreteHandler，总经理
        public class President : Approver
        {
            public President(string name)
                : base(name)
            {}

            //少于100000可以决定
            public override void ProcessRequest(PurchaseRequest request)
            {
                if (request.Amount < 100000.0)
                {
                    Console.WriteLine("{0}：{1}少于10000块，{2}可以批准！", request.ProductName, request.Amount, Name);
                }
                else
                {
                    Console.WriteLine("需要组织一个会议讨论");
                }
            }
        }
    }
}