Design Pattern ->Factory Method

Layering & Contract Philosophy With additional indirection

Factory Method

The example code is as following:

 

 1 class CProduct //interface declaration
 2 class CConcreteProductOne: public CProduct;
 3 class CConcreteProductTwo: public CProduct;
 4 
 5 
 6 class CCreator
 7 {
 8      public: virtual CProduct* FactoryMethod()= 0;
 9 }
10 class CConcreteCreator: public CCreator
11 {
12      public: CProduct* FactoryMethod(){ return new CConcreteProductOne()  OR  new CConcreteProductTwo()};
13 }
14 class CClient
15 {  
16         CCreator *pCreator = new CConreteCreator();
17         CProduct *pProduct = pCreator->FacotryMethod();
18 }

IoC = Inversion Of Control.

控制反转还有一个名字叫做依赖注入(Dependency Injection)。简称DI

DIP = Dependence-Inversion Principle ( low-level module is depended on high-level module by defining abstract interface in high-level).

Interface-Oriented Programming, not Implement-Oriented Programming

Applicability
Use the Factory Method pattern when

  •  A class can't anticipate the class of objects it must create.
  •  A class wants its subclasses to specify the objects it creates.
  • Classes delegate responsibility to one of several helper subclasses, and you want to localize the knowledge of which helper subclass is the delegate.
  • The new proper/appropriate instance of the concrete product can be got at run-time from the real situation.

Participants

  • Product: defines the interface of objects the factory method creates.
  • ConcreteProduct : implements the Product interface.
  • Creator : 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 ConcreteProduct object. may call the factory method to create a Product object.
  • ConcreteCreator: overrides the factory method to return an instance of a ConcreteProduct.

Collaborations

  • Creator relies on its subclasses to define the factory method so that it returns an instance of the appropriate ConcreteProduct.
posted @ 2013-07-30 08:58  iDragon  阅读(242)  评论(0编辑  收藏  举报