FactoryMethod工厂方法(创建型模式)
最近看了李建宗老师的面向对象的设计模式的课程。我把里面的代码记录了下来以供大家参考。其中有的地方我整理了一下,可能有的地方和课程里的不一样。
动机:
在软件系统中,经常面临着“某个对象”的创建工作;由于需求的变化,这个对象经常面临着剧烈的变化,但是它却拥有比较稳定的接口。
如何应对这种变化?如何提供一种“封闭机制”来隔离出“这个易变对象”的变化,从而保持系统中“其他依赖该对象”不随着需求改变而改变?
意图:
定义一个用于创建对象的接口,让子类决定实例化哪一个类。Factory Method使得一个类的实例化延迟到子类。
出自:《设计模式》GoF
Factory Method模式的几个要点:
1、Factory Method模式主要用于隔离类对象的使用者和具体类型之间的耦合关系。面对一个经常变化的具体类型,紧耦合关系会导致软件的脆弱。
2、Factory Method模式通过面向对象的手法,将所要创建的具体对象工作延迟到子类,从面实现一个种扩展(而非更改)的策略,较好地解决了这种对耦合关系。
3、Factory Method模式解决“单个对象”的需求变化,Abstract Factory模式解决“系列对象”的需求变化,Builder模式解决“对象部分”的需求变化。
识别工厂方法模式:
工厂方法模式需要包括一个操作,这个操作创建了一个对象,同时也使客户无需了解应该具体实例化哪个类.
稳定部分代码:
动机:
在软件系统中,经常面临着“某个对象”的创建工作;由于需求的变化,这个对象经常面临着剧烈的变化,但是它却拥有比较稳定的接口。
如何应对这种变化?如何提供一种“封闭机制”来隔离出“这个易变对象”的变化,从而保持系统中“其他依赖该对象”不随着需求改变而改变?
意图:
定义一个用于创建对象的接口,让子类决定实例化哪一个类。Factory Method使得一个类的实例化延迟到子类。
出自:《设计模式》GoF
Factory Method模式的几个要点:
1、Factory Method模式主要用于隔离类对象的使用者和具体类型之间的耦合关系。面对一个经常变化的具体类型,紧耦合关系会导致软件的脆弱。
2、Factory Method模式通过面向对象的手法,将所要创建的具体对象工作延迟到子类,从面实现一个种扩展(而非更改)的策略,较好地解决了这种对耦合关系。
3、Factory Method模式解决“单个对象”的需求变化,Abstract Factory模式解决“系列对象”的需求变化,Builder模式解决“对象部分”的需求变化。
识别工厂方法模式:
工厂方法模式需要包括一个操作,这个操作创建了一个对象,同时也使客户无需了解应该具体实例化哪个类.
稳定部分代码:
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using System;
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namespace NameFactory
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{
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/// <summary>
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/// Summary description for Namer.
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/// </summary>
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//Base class for getting split names
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public class Namer {
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//parts stored here
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protected string frName, lName;
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//return first name
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public string getFrname(){
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return frName;
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}
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//return last name
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public string getLname() {
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return lName;
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}
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}
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}
具体类
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using System;
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namespace NameFactory
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{
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/// <summary>
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/// Summary description for FirstFirst.
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/// </summary>
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public class FirstFirst : Namer
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{
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public FirstFirst(string name)
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{
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int i = name.IndexOf (" ");
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if(i > 0) {
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frName = name.Substring (0, i).Trim ();
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lName = name.Substring (i + 1).Trim ();
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}
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else {
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lName = name;
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frName = "";
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}
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}
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}
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public class LastFirst : Namer
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{
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public LastFirst(string name) {
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int i = name.IndexOf (",");
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if(i > 0) {
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lName = name.Substring (0, i);
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frName = name.Substring (i + 1).Trim ();
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}
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else {
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lName = name;
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frName = "";
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}
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}
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}
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}
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实例化:
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using System;
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namespace NameFactory
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{
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/// <summary>
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/// Summary description for NameFactory.
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/// </summary>
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public class NameFactory {
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public NameFactory() {}
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public Namer getName(string name) {
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int i = name.IndexOf (",");
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if(i > 0)
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return new LastFirst (name);
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else
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return new FirstFirst (name);
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}
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}
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}
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主程序
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using System;
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using System.Drawing;
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using System.Collections;
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using System.ComponentModel;
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using System.Windows.Forms;
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using System.Data;
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namespace NameFactory
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{
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/// <summary>
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/// Summary description for Form1.
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/// </summary>
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public class Form1 : System.Windows.Forms.Form
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{
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private System.Windows.Forms.Label label1;
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private System.Windows.Forms.Button btCompute;
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private System.Windows.Forms.Label label2;
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private System.Windows.Forms.Label label3;
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private System.Windows.Forms.TextBox txFirst;
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private NameFactory nameFact;
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private System.Windows.Forms.TextBox txName;
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private System.Windows.Forms.TextBox txLast;
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/// <summary>
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/// Required designer variable.
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/// </summary>
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private System.ComponentModel.Container components = null;
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private void init() {
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nameFact = new NameFactory ();
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}
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public Form1()
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{
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//
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// Required for Windows Form Designer support
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//
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InitializeComponent();
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init();
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//
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// TODO: Add any constructor code after InitializeComponent call
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//
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}
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/// <summary>
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/// Clean up any resources being used.
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/// </summary>
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protected override void Dispose( bool disposing )
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{
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if( disposing )
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{
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if (components != null)
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{
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components.Dispose();
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}
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}
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base.Dispose( disposing );
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}
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/// <summary>
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/// The main entry point for the application.
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/// </summary>
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[STAThread]
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static void Main()
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{
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Application.Run(new Form1());
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}
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private void btCompute_Click(object sender, System.EventArgs e) {
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Namer nm = nameFact.getName (txName.Text );
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txFirst.Text = nm.getFrname ();
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txLast.Text = nm.getLname ();
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}
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}
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}
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