二十四种设计模式:策略模式(Strategy Pattern)
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策略模式(Strategy Pattern)
介绍
定义一系列的算法,把它们一个个封装起来,并且使它们可相互替换。本模式使得算法的变化可独立于使用它的客户。
示例
有一个Message实体类,对它的操作有Insert()和Get()方法,持久化数据在SqlServer数据库中或Xml文件里(两种可互换的算法)。由客户端决定使用哪种算法。
MessageModel
using System; using System.Collections.Generic; using System.Text; namespace Pattern.Strategy { /// <summary> /// Message实体类 /// </summary> public class MessageModel { /// <summary> /// 构造函数 /// </summary> /// <param name="msg">Message内容</param> /// <param name="pt">Message发布时间</param> public MessageModel(string msg, DateTime pt) { this._message = msg; this._publishTime = pt; } private string _message; /// <summary> /// Message内容 /// </summary> public string Message { get { return _message; } set { _message = value; } } private DateTime _publishTime; /// <summary> /// Message发布时间 /// </summary> public DateTime PublishTime { get { return _publishTime; } set { _publishTime = value; } } } }
IMessageStrategy
using System; using System.Collections.Generic; using System.Text; namespace Pattern.Strategy { /// <summary> /// 策略接口 /// </summary> public interface IMessageStrategy { /// <summary> /// 获取Message /// </summary> /// <returns></returns> List<MessageModel> Get(); /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> bool Insert(MessageModel mm); } }
SqlMessage
using System; using System.Collections.Generic; using System.Text; namespace Pattern.Strategy { /// <summary> /// Sql方式操作Message /// </summary> public class SqlMessage : IMessageStrategy { /// <summary> /// 获取Message /// </summary> /// <returns></returns> public List<MessageModel> Get() { List<MessageModel> l = new List<MessageModel>(); l.Add(new MessageModel("SQL方式获取Message", DateTime.Now)); return l; } /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public bool Insert(MessageModel mm) { // 代码略 return true; } } }
XmlMessage
using System; using System.Collections.Generic; using System.Text; namespace Pattern.Strategy { /// <summary> /// Xml方式操作Message /// </summary> public class XmlMessage : IMessageStrategy { /// <summary> /// 获取Message /// </summary> /// <returns></returns> public List<MessageModel> Get() { List<MessageModel> l = new List<MessageModel>(); l.Add(new MessageModel("XML方式获取Message", DateTime.Now)); return l; } /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public bool Insert(MessageModel mm) { // 代码略 return true; } } }
Message
using System; using System.Collections.Generic; using System.Text; namespace Pattern.Strategy { /// <summary> /// Context类 /// </summary> public class Message { /// <summary> /// 声明一个IMessageStrategy类型 /// </summary> private IMessageStrategy _strategy; /// <summary> /// 构造函数 /// </summary> /// <param name="strategy">具体算法</param> public Message(IMessageStrategy strategy) { this._strategy = strategy; } /// <summary> /// 获取Message /// </summary> /// <returns></returns> public List<MessageModel> Get() { return _strategy.Get(); } /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public bool Insert(MessageModel mm) { return _strategy.Insert(mm); } } }
Client
using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.htmlControls; using Pattern.Strategy; public partial class Strategy : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Message m = new Message(new XmlMessage()); Response.Write(m.Insert(new MessageModel("插入", DateTime.Now))); Response.Write("<br />"); Response.Write(m.Get()[0].Message + " " + m.Get()[0].PublishTime.ToString()); Response.Write("<br />"); m = new Message(new SqlMessage()); Response.Write(m.Insert(new MessageModel("插入", DateTime.Now))); Response.Write("<br />"); Response.Write(m.Get()[0].Message + " " + m.Get()[0].PublishTime.ToString()); Response.Write("<br />"); } }
运行结果
True
XML方式获取Message 2007-2-10 22:42:44
True
SQL方式获取Message 2007-2-10 22:42:44
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