设计模式一 - Simple Factory, Factory Method, Abstract Factory以及Builder模式简述
虽然现在博客园上关于设计模式的文章已经有很多，但还是写一篇来凑下热闹，也算是对自己多这几种模式得使用总结。
Factory Pattern 工厂模式和 Builder Patter 建造者模式都是通过定义接口来将类的定义和实现区分开来。下面一步一步来做说明
1. Simple Factory 简单工厂
简单工厂只是将类简单抽象化，以Pizza为例，我们定义好Pizza的接口，实现继承Pizza的类PizzaA和PizzaB，然后简单工厂提供方法根据传进来的参数类型确定像调用者返回PizzaA或者PizzaB的实例
代码
{
void DoPizza();
}
public class PizzaA : Pizza
{
public void DoPizza()
{
Console.WriteLine("pizza A");
}
}
public class PizzaB : Pizza
{
public void DoPizza()
{
Console.WriteLine("pizza B");
}
}
public static class SimplePizzaFacotry
{
public static Pizza Create(string type)
{
if (type == "PizzaA")
return new PizzaA();
else
return new PizzaB();
}
}
// Usage
public class SimplePizzaFacotryOrder
{
public void OrderPizza()
{
Pizza pizza = SimplePizzaFacotry.Create("PizzaA");
pizza.DoPizza();
}
}
2. Factory Method工厂方法
工厂方式是在简单工厂模式基础上进一步抽象来符合OO设计的要求。这里将Factory抽象化为接口或抽象类，然后继承类负责具体实现。此时增加一个FactoryManage来负责返回那个工厂类实现的实例。代码示例如下
代码public abstract class PizzaFactory
{
public abstract Pizza Create();
}
public class PizzaAFactory : PizzaFactory
{
public override Pizza Create()
{
return new PizzaA();
//throw new NotImplementedException();
}
}
public class PizzaBFactory : PizzaFactory
{
public override Pizza Create()
{
return new PizzaB();
//throw new NotImplementedException();
}
}
public abstract class PizzaMethodManager
{
public static PizzaFactory Factory = new PizzaAFactory();
}
//usage
public class FactoryMethodPizzaOrder
{
public FactoryMethodPizzaOrder()
{
Pizza pizza = PizzaMethodManager.Factory.Create();
}
}
3. Abstract Factory 抽象工厂
抽象工厂和工厂方法基本上一样，区别在于此时抽象工厂可以来实现一系列相关类的实现。继续用Pizza举例，这里将Pizza分为Dough和Sauce即面团和酱，然后定义HutPizza和PapaPizza的面团Dougn, Sauce以及Pizza的实现。示例如下
代码{
void DoDough();
}
public interface ISauce
{
void DoSauce();
}
public class PapaDough : IDough
{
public void DoDough()
{
Console.WriteLine("Papa Jone's Dough");
}
}
public class PapaSource : ISauce
{
public void DoSauce()
{
Console.WriteLine("Papa Jone's Sauce");
}
}
public class HutDough : IDough
{
public void DoDough()
{
Console.WriteLine("Pizza Hut's Dough");
}
}
public class HutSource : ISauce
{
public void DoSauce()
{
Console.WriteLine("Pizza Hut's Sauce");
}
}
public interface IPizzaFactory
{
IDough PrepareDough();
ISauce AddSauce();
}
public class PapaPizzaFacotry : IPizzaFactory
{
public IDough PrepareDough()
{
return new PapaDough();
}
public ISauce AddSauce()
{
return new PapaSource();
}
}
public class HutPizzaFacotry : IPizzaFactory
{
public IDough PrepareDough()
{
return new HutDough();
}
public ISauce AddSauce()
{
return new HutSource();
}
}
public abstract class AbstractPizzaManager
{
public static IPizzaFactory Facotry = new PapaPizzaFacotry();
}
// Usage
public class OrderPizzaAbstract
{
public void OrderPizza()
{
IDough dough = AbstractPizzaManager.Facotry.PrepareDough();
ISauce sauce = AbstractPizzaManager.Facotry.AddSauce();
dough.DoDough();
sauce.DoSauce();
}
}
4. Builder Pattern 建造者模式
Builder和抽象工厂类似，也是建立一系列对象的实现。区别在于Builder建立的一对象有依赖关系而Factory的对象只是有关联。依旧以Pizza为例，pizza的做法是先做面团(饼底)，然后放Sauce(Cheese或者其他的东西)，然后放Topping(火腿，香肠之类的)。举例如下
代码{
public string Dough { get; set; }
public string Sauce { get; set; }
public string Topping { get; set; }
}
abstract class PizzaBuilder
{
public PizzaBD pizza { get; protected set; }
public void CreatePizza()
{
pizza = new PizzaBD();
}
public abstract void BuildDough();
public abstract void BuildSauce();
public abstract void BuildTopping();
}
class HawaiianPizzaBuilder : PizzaBuilder
{
public override void BuildDough()
{
pizza.Dough = "Cross";
}
public override void BuildSauce()
{
pizza.Sauce = "Mild";
}
public override void BuildTopping()
{
pizza.Topping = "Ham+Pineapple";
}
}
class SpicyPizzaBuilder : PizzaBuilder
{
public override void BuildDough()
{
pizza.Dough = "Pan Baked";
}
public override void BuildSauce()
{
pizza.Sauce = "Hot";
}
public override void BuildTopping()
{
pizza.Topping = "Pepperoni+Salami";
}
}
class Cook
{
public PizzaBuilder PizzaBuilder { get; set; }
public PizzaBD Pizza { get { return PizzaBuilder.pizza; } }
public void MakePizza()
{
PizzaBuilder.CreatePizza();
PizzaBuilder.BuildDough();
PizzaBuilder.BuildSauce();
PizzaBuilder.BuildTopping();
}
}
// usage
public class CallBuilder
{
public void OrderPizza()
{
Cook cook = new Cook();
cook.PizzaBuilder = new SpicyPizzaBuilder();
cook.MakePizza();
cook.PizzaBuilder = new HawaiianPizzaBuilder();
cook.MakePizza();
}
}
5. Facade Pattern 外观模式
提到了Builder模式，也就顺便提一下Facade模式。两者类似处在于都是建立一系列对象，区别在于Builder模式创建一系列有依赖关系的子类，而Facade模式则是建立一个将复杂的子类简化和集中化的通道。还是以Pizza为例，客户吃完付款，需要Waiter收取现金/卡，然后财务做账/transfer之后打印发票，返回。对客户来说后端多的一系列动作他并不关心，PizzaPayFacade提供给客户一个Pay方法，方法里面完成这一系列的动作[可能包括类的实现]。代码稍后提供。大家可以先参考First We try, then we trust的Facade说明的代码示例 http://www.cnblogs.com/zhenyulu/articles/55992.html
