CSharp设计模式读书笔记（24）：访问者模式(学习难度：★★★★☆，使用频率：★☆☆☆☆)

模式角色与结构：

示例代码：

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

namespace CSharp.DesignPattern.VisitorPattern
{
    class Program
    {
        static void Main(string[] args)
        {
            ObjectStructure list = new ObjectStructure();
            list.AddEmployee(new FulltimeEmployee("Mike", 2000));
            list.AddEmployee(new FulltimeEmployee("Tony", 3000));
            list.AddEmployee(new ParttimeEmployee("Nancen", 800));
            list.AddEmployee(new ParttimeEmployee("Bibo", 500));

            FinanceVisitor fVisitor = new FinanceVisitor();
            HrVisitor hVisitor = new HrVisitor();

            list.Accept(fVisitor);
            list.Accept(hVisitor);
        }
    }

    class ObjectStructure
    {
        public void Accept(Visitor visitor)
        {
            foreach (IEmployee element in employees)
            {
                element.Accept(visitor);
            }
        }

        public void AddEmployee(IEmployee employee)
        {
            employees.Add(employee);
        }

        public void RemoveEmployee(IEmployee employee)
        {
            employees.Remove(employee);
        }

        private List<IEmployee> employees = new List<IEmployee>();
    }

    class Visitor
    {
        public abstract void Visit(FulltimeEmployee fulltime);
        public abstract void Visit(ParttimeEmployee contract);
    }

    class FinanceVisitor : Visitor
    {
        public void Visit(FulltimeEmployee fulltime)
        {
            Console.Write("The wage of fulltime is ..."); 
        }
        public void Visit(ParttimeEmployee contract)
        {
            Console.Write("The wage of parttime is ..."); 
        }
    }

    class HrVisitor : Visitor
    {
        public void Visit(FulltimeEmployee fulltime)
        {
            Console.Write("The worktime of fulltime is ...");
            Console.Write("The overtime of fulltime is ...");
            Console.Write("The timeoff of fulltime is ..."); 
        }
        public void Visit(ParttimeEmployee contract)
        {
            Console.Write("The worktime of fulltime is ..."); 
        }
    }

    interface IEmployee
    {
        public void Accept(Visitor visitor)
        { }

        String Name { set; get; }
        Int32 Wage { set; get; }
    }

    class FulltimeEmployee : IEmployee
    {
        public FulltimeEmployee(String name, Int32 wage)
        {
            this._name = name;
            this._wage = wage;
        }

        public void Accept(Visitor visitor)
        {
            visitor.Visit(this);
        }

        public void OperationFulltime()
        { }

        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        public int Wage
        {
            get { return _wage; }
            set { _wage = value; }
        }

        private String _name;
        private Int32 _wage;
    }

    class ParttimeEmployee : IEmployee
    {
        public ParttimeEmployee(String name, Int32 wage)
        {
            this._name = name;
            this._wage = wage;
        }

        public void Accept(Visitor visitor)
        {
            visitor.Visit(this);
        }

        public void OperationParttime()
        { }

        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        public int Wage
        {
            get { return _wage; }
            set { _wage = value; }
        }

        private String _name;
        private Int32 _wage;
    }
}