第一眼看到builder模式,就覺得眼熟,和我們前面將的抽象工廠模式非常相近,我想不可能相同的模式用兩個不同的名字,於是就有了下面的一些火花了.
Builder模式定義:
將一個複雜對象的構建與它的表示分離,使得同樣的構建過程可以創建不同的表示
這個翻譯就很模糊,看了,跟沒看一樣,可是這是網上目前最多的翻譯了,所以也不想去理解他了,反正心裏希望翻譯這句話的人一路走好.所以說那些翻譯國外文章的人一定要注意了,如果你們自己都沒弄懂的話,千萬不要翻出來,害大家.
下面用原文來表述吧:
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.(簡述:隱藏了對象構造的細節)
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.(下面的例子是一個建造房屋的例子,客戶用 buildhouse(Boolean blnbackyard) 來建造房屋,
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();//取得後院的引用
long NoOfRooms();//房子數
string Discription();//房子的描述
}
public class CApt:Ihouse//沒有後院的房子
{ 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;//關鍵,沒有後院.
}
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;//有後院
}
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//房間接口.
{
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來總體控制用什麼builder來造.
{
if (blnBackyard)
{
return new CSFH();//造有後院的房子
}
else
{
return new CApt(); //造沒有後院的房子
}
}
}
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());
}
}