工厂方法模式

1.       定义

           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。工厂方法是一个类的实例化延迟到其子类。

2.      UML 类图

 

3.      结构代码

// Factory Method pattern -- Structural example

using System;   namespace DoFactory.GangOfFour.Factory.Structural {   /// <summary>   /// MainApp startup class for Structural   /// Factory Method Design Pattern.   /// </summary>   class MainApp   {     /// <summary>     /// Entry point into console application.     /// </summary>     static void Main()     {       // An array of creators       Creator[] creators = new Creator[2];         creators[0] = new ConcreteCreatorA();       creators[1] = new ConcreteCreatorB();         // Iterate over creators and create products       foreach (Creator creator in creators)       {         Product product = creator.FactoryMethod();         Console.WriteLine("Created {0}",           product.GetType().Name);       }         // Wait for user       Console.ReadKey();     }   }     /// <summary>   /// The 'Product' abstract class   /// </summary>   abstract class Product   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class ConcreteProductA : Product   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class ConcreteProductB : Product   {   }     /// <summary>   /// The 'Creator' abstract class   /// </summary>   abstract class Creator   {     public abstract Product FactoryMethod();   }     /// <summary>   /// A 'ConcreteCreator' class   /// </summary>   class ConcreteCreatorA : Creator   {     public override Product FactoryMethod()     {       return new ConcreteProductA();     }   }     /// <summary>   /// A 'ConcreteCreator' class   /// </summary>   class ConcreteCreatorB : Creator   {     public override Product FactoryMethod()     {       return new ConcreteProductB();     }   } }

Output Created ConcreteProductA Created ConcreteProductB

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4.      实例代码

// Factory Method pattern -- Real World example

using System; using System.Collections.Generic;   namespace DoFactory.GangOfFour.Factory.RealWorld {   /// <summary>   /// MainApp startup class for Real-World   /// Factory Method Design Pattern.   /// </summary>   class MainApp   {     /// <summary>     /// Entry point into console application.     /// </summary>     static void Main()     {       // Note: constructors call Factory Method       Document[] documents = new Document[2];         documents[0] = new Resume();       documents[1] = new Report();         // Display document pages       foreach (Document document in documents)       {         Console.WriteLine("\n" + document.GetType().Name + "--");         foreach (Page page in document.Pages)         {           Console.WriteLine(" " + page.GetType().Name);         }       }         // Wait for user       Console.ReadKey();     }   }     /// <summary>   /// The 'Product' abstract class   /// </summary>   abstract class Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class SkillsPage : Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class EducationPage : Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class ExperiencePage : Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class IntroductionPage : Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class ResultsPage : Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class ConclusionPage : Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class SummaryPage : Page   {   }     /// <summary>   /// A 'ConcreteProduct' class   /// </summary>   class BibliographyPage : Page   {   }     /// <summary>   /// The 'Creator' abstract class   /// </summary>   abstract class Document   {     private List<Page> _pages = new List<Page>();       // Constructor calls abstract Factory method     public Document()     {       this.CreatePages();     }       public List<Page> Pages     {       get { return _pages; }     }       // Factory Method     public abstract void CreatePages();   }     /// <summary>   /// A 'ConcreteCreator' class   /// </summary>   class Resume : Document   {     // Factory Method implementation     public override void CreatePages()     {       Pages.Add(new SkillsPage());       Pages.Add(new EducationPage());       Pages.Add(new ExperiencePage());     }   }     /// <summary>   /// A 'ConcreteCreator' class   /// </summary>   class Report : Document   {     // Factory Method implementation     public override void CreatePages()     {       Pages.Add(new IntroductionPage());       Pages.Add(new ResultsPage());       Pages.Add(new ConclusionPage());       Pages.Add(new SummaryPage());       Pages.Add(new BibliographyPage());     }   } }

Output Resume -------  SkillsPage  EducationPage  ExperiencePage Report -------  IntroductionPage  ResultsPage  ConclusionPage  SummaryPage  BibliographyPage

该文章来自：http://www.dofactory.com/Patterns/PatternFactory.aspx