Factory Method Design Pattern -- Design Pattern

  Define an interface for creating an object, but let sub classes decide which class to instantiate. Factory Method lets a class defer instantiate to sub classes.

Participants

    The classes and/or objects participating in this pattern are:

• Product  (Page)

       Defines the interface of objects the factory method creates

• Concrete Product  (SkillsPage, EducationPage, ExperiencePage)

        Implements the Product interface

• Creator  (Document)

         Declares the factory method, which returns an object of type Product. Creator may also define a default implementation of the factory method that returns a default Concrete Product object. May call the factory method to create a Product object.

• Concrete Creator (Report, Resume)

Overrides the factory method to return an instance of a Concrete Product.

Code Sample:

using System;

namespace 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