软件工程 设计模式学习之工厂方法模式Factory Method

在现实生活中我们可以看见,乐事在卖薯片,可比克也在卖.
我敢肯定的说它们各自都有自己的工厂来生产薯片,而且生产出来的薯片味道还是不一样的.
这就是我们这里所谓的工厂方法模式. 我们来看看这个模式的UML图:

这个模式中我们可以看到:
产品和工厂2个基类,然后它们下面又有些子孙类.
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现在进入我们的代码环节了,首先上场的是PHP. 

 1 //抽象产品   
 2 abstract class Product{   
 3     abstract function Test();   
 4 }   
 5   
 6 class leshi extends Product {   
 7     public function Test() {   
 8         echo("Leshi!\n");   
 9     }   
10 }   
11 class kebike extends Product {   
12     public function Test() {   
13         echo("Kebike!\n");   
14     }   
15 }   
16 //抽象工厂   
17 abstract class Factory{   
18     abstract function GetProduct();   
19 }   
20   
21 class leshiFactory extends Factory{     
22     public function GetProduct() {   
23         return new leshi();   
24     }   
25 }   
26 class kebikeFactory extends  Factory{   
27     public function GetProduct() {   
28         return new kebike();   
29     }   
30 }   
31 //首先我们先建立两个公司的工厂.   
32 $leshiF = new leshiFactory();   
33 $kebikeF = new kebikeFactory();   
34 //每个工厂给我出10包薯片   
35 for($i=0;$i<10;$i++){   
36     $leshiF->GetProduct()->Test();   
37     $kebikeF->GetProduct()->Test();   
38 }  
39 
40 //抽象产品
41 abstract class Product{
42     abstract function Test();
43 }
44 
45 class leshi extends Product {
46     public function Test() {
47         echo("Leshi!\n");
48     }
49 }
50 class kebike extends Product {
51     public function Test() {
52         echo("Kebike!\n");
53     }
54 }
55 //抽象工厂
56 abstract class Factory{
57     abstract function GetProduct();
58 }
59 
60 class leshiFactory extends Factory{  
61     public function GetProduct() {
62         return new leshi();
63     }
64 }
65 class kebikeFactory extends  Factory{
66     public function GetProduct() {
67         return new kebike();
68     }
69 }
70 //首先我们先建立两个公司的工厂.
71 $leshiF = new leshiFactory();
72 $kebikeF = new kebikeFactory();
73 //每个工厂给我出10包薯片
74 for($i=0;$i<10;$i++){
75     $leshiF->GetProduct()->Test();
76     $kebikeF->GetProduct()->Test();
77 }
78 
79 

和简单工厂模式有点儿像,但是那个只有一个工厂实例,
而我们这里是有多少种产品就有多少个工厂实例
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 C#粉墨登场:

namespace FactoryMethod_DesignPattern   
{   
    using System;   
  
    // These two classes could be part of a framework,   
    // which we will call DP   
    // ===============================================   
       
    class DPDocument    
    {   
       
  
    }   
  
    abstract class DPApplication    
    {   
        protected DPDocument doc;   
           
        abstract public void CreateDocument();   
  
        public void ConstructObjects()   
        {   
               
            // Create objects as needed   
            // . . .   
  
            // including document   
            CreateDocument();   
        }          
        abstract public void Dump();   
    }   
  
    // These two classes could be part of an application    
    // =================================================   
  
    class MyApplication : DPApplication    
    {   
        override public void CreateDocument()   
        {   
            doc = new MyDocument();            
        }              
  
        override public void Dump()   
        {   
            Console.WriteLine("MyApplication exists");   
        }   
    }      
  
    class MyDocument : DPDocument    
    {   
  
    }   
  
    /// <SUMMARY></SUMMARY>   
    ///    Summary description for Client.   
    ///    
    public class Client   
    {   
        public static int Main(string[] args)   
        {   
            MyApplication myApplication = new MyApplication();   
  
            myApplication.ConstructObjects();   
  
            myApplication.Dump();   
               
            return 0;   
        }   
    }   
}  

namespace FactoryMethod_DesignPattern
{
    using System;

 // These two classes could be part of a framework,
 // which we will call DP
 // ===============================================
 
 class DPDocument 
 {
 

 }

 abstract class DPApplication 
 {
  protected DPDocument doc;
  
  abstract public void CreateDocument();

  public void ConstructObjects()
  {
   
   // Create objects as needed
   // . . .

   // including document
   CreateDocument();
  }  
  abstract public void Dump();
 }

 // These two classes could be part of an application 
 // =================================================

 class MyApplication : DPApplication 
 {
  override public void CreateDocument()
  {
   doc = new MyDocument();   
  }   

  override public void Dump()
  {
   Console.WriteLine("MyApplication exists");
  }
 } 

 class MyDocument : DPDocument 
 {

 }

    /// 
    ///    Summary description for Client.
    /// 
    public class Client
    {
        public static int Main(string[] args)
        {
            MyApplication myApplication = new MyApplication();

   myApplication.ConstructObjects();

   myApplication.Dump();
   
            return 0;
        }
    }
}

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Delphi王者驾临!

IProduct = interface 
    procedure Test; 
  end; 

  IFactory = interface 
    function GetProduct:IProduct; 
  end; 

  TLeShi = class(TInterfacedObject,IProduct) 
  public 
    procedure Test; 
  end; 

  TKeBiKe = class(TInterfacedObject,IProduct) 
  public 
    procedure Test; 
  end; 

  TLeShiFactory = class(TInterfacedObject,IFactory) 
  public 
    function GetProduct:IProduct; 
  end; 

  TKeBiKeFactory = class(TInterfacedObject,IFactory) 
  public 
    function GetProduct:IProduct; 
  end; 

var 
  Form1: TForm1; 

implementation 

{$R *.dfm} 

{ TKeBiKeFactory } 

function TKeBiKeFactory.GetProduct: IProduct; 
begin 
  Result:=TKeBiKe.Create; 
end; 

{ TLeShi } 

procedure TLeShi.Test; 
begin 
  ShowMessage('LeShi!'); 
end; 

{ TKeBiKe } 

procedure TKeBiKe.Test; 
begin 
  ShowMessage('KeBiKe'); 
end; 

{ TLeShiFactory } 

function TLeShiFactory.GetProduct: IProduct; 
begin 
  Result:=TLeShi.Create; 
end; 

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给乐事和可比克打了广告不知道能不能得到点儿广告费哟..哈哈.
我们最后看看这个模式的适用性:

当一个类不知道它所必须创建的对象的类的时候。
当一个类希望由它的子类来指定它所创建的对象的时候。
当类将创建对象的职责委托给多个帮助子类中的某一个，并且你希望将哪一个帮助子类是代理者这一信息局部化的时候。