builder 模式

第一眼看到builder模式,就觉得眼熟,和我们前面将的抽象工厂模式非常相近,我想不可能相同的模式用两个不同的名字,于是就有了下面的一些火花了.

Builder模式定义:
将一个复杂对象的构建与它的表示分离,使得同样的构建过程可以创建不同的表示

这个翻译就很模糊,看了,跟没看一样,可是这是网上目前最多的翻译了,所以也不想去理解他了,反正心里希望翻译这句话的人一路走好.所以说那些翻译国外文章的人一定要注意了,如果你们自己都没弄懂的话,千万不要翻出来,害大家.

下面用原文来表述吧:

The Builder pattern allows a client object to construct a complex object by specifying only its type and content. The client is shielded from the details of the object’s construction.(简述:隐藏了对象构造的细节)

It is a pattern for step-by-step creation of a complex object so that the same construction process can create different representations is the routine in the builder pattern that also makes for finer control over the construction process. All the different builders generally inherit from an abstract builder class that declares the general functions to be used by the director to let the builder create the product in parts.

Builder has a similar motivation to the abstract factory but, whereas in that pattern, the client uses the abstract factory class methods to create its own object, in Builder the client instructs the builder class on how to create the object and then asks it for the result. How the class is put together is up to the Builder class. It's a subtle difference.

The Builder pattern is applicable when the algorithm for creating a complex object should be independent of the parts that make up the object and how they are assembled and the construction process must allow different representations for the object that’s constructed

Example

Below is an example of creating a House, the clients asks the Director (CDirector class) to create a House by calling BuildHouse method which takes a boolean parameter (blnBackyard), the director then creates an Apartment (Concrete Builder) if the blnBackyard is false or a Single Family Home (Concrete Builder) if the blnBackyard is true (both of them implements IHouse interface) and returns IHouse (Abstract Builder) Interface.(下面的例子是一个建造房屋的例子,客户用 buildhouse(Boolean blnbackyard) 来建造房屋,

The director does the complex building of a House and the client gets back IHouse interface that it codes against without worrying about the creation of House, Rooms, backyard etc.

 

C#

using System;
using System.Collections;

public interface Ihouse//房子的接口
{
   bool GetBackyard();//取得后院的引用
   long NoOfRooms();//房子数
   string  Discription();//房子的描述
}

public class CApt:Ihouse//没有后院的房子
{   private bool mblnBackyard;
   private Hashtable Rooms;
   public CApt()//
   {   CRoom room;
      Rooms = new Hashtable();
      room = new CRoom();
      room.RoomName = "Master Bedroom";
      Rooms.Add ("room1",room);

      room = new CRoom();
        room.RoomName = "Second Bedroom";
      Rooms.Add ("room2",room);

      room = new CRoom();
      room.RoomName = "Living Room";
      Rooms.Add ("room3",room);
     
      mblnBackyard = false;//关键,没有后院.
   }

   public bool GetBackyard()
   {
      return mblnBackyard;
   }
   public long NoOfRooms()
   {
      return Rooms.Count;
   }
   public string  Discription()
   {
      IDictionaryEnumerator myEnumerator  =
                      Rooms.GetEnumerator();
        string strDiscription;
        strDiscription = "This is an Apartment with " +
                         Rooms.Count + " Rooms /n";
        strDiscription = strDiscription +
             "This Apartment doesn't have a backyard /n";
      while (myEnumerator.MoveNext())
      {
         strDiscription = strDiscription + "/n" +
                 myEnumerator.Key + "/t" +
                 ((CRoom)myEnumerator.Value).RoomName;
      }
        return strDiscription;
   }
}

public class CSFH:IHouse
{   private bool mblnBackyard;
   private Hashtable Rooms;
   public CSFH()
   {
      CRoom room;
      Rooms = new Hashtable();

      room = new CRoom();
      room.RoomName = "Master Bedroom";
      Rooms.Add ("room1",room);

      room = new CRoom();
      room.RoomName = "Second Bedroom";
      Rooms.Add ("room2",room);

      room = new CRoom();
      room.RoomName = "Third Room";
      Rooms.Add ("room3",room);
     
      room = new CRoom();
      room.RoomName = "Living Room";
      Rooms.Add ("room4",room);

      room = new CRoom();
      room.RoomName = "Guest Room";
      Rooms.Add ("room5",room);

      mblnBackyard = true;//有后院
 
   }

   public bool GetBackyard()
   {
      return mblnBackyard;
   }
   public long NoOfRooms()
   {
      return Rooms.Count;
   }
   public string  Discription()
   {
     IDictionaryEnumerator myEnumerator  =
                         Rooms.GetEnumerator();
     string strDiscription;
     strDiscription = "This is an Single Family Home with "
                      + Rooms.Count + " Rooms /n";
     strDiscription = strDiscription +
                          "This house has a backyard /n";
       while (myEnumerator.MoveNext())
     {
        strDiscription = strDiscription +
                "/n" + myEnumerator.Key + "/t" +
                ((CRoom)myEnumerator.Value).RoomName;
     }     
     return strDiscription;
   }
}

public interface Iroom//房间接口.
{
   string RoomName{get;set;}
}

public class CRoom:IRoom
{
   private string mstrRoomName;
   public string RoomName
   {
      get
      {
         return mstrRoomName;
      }
      set
      {
         mstrRoomName = value;
      }
   }
}

public class CDirector
{
   public IHouse BuildHouse(bool blnBackyard)//返回不同的房子的.builder,director来总体控制用什么builder来造.
   {
      if (blnBackyard)
      {
         return new CSFH();//造有后院的房子
      }
      else
      {
         return new CApt(); //造没有后院的房子
      }
   }
}

public class Client
{
  static void Main(string[] args)
  {
    CDirector objDirector = new CDirector();
    IHouse objHouse;
    objHouse = objDirector.BuildHouse(bool.Parse(args[0]));
    Console.WriteLine(objHouse.Discription());
  }
}