在petshop4.0中也用到了几个常用的设计模式:简单工厂模式,工厂方法模式,策略模式,并附之返射与配置文件.下面就来用我自己的理解用大白话说出来.
1.简单工厂模式.
比如A与B一起写代码,A负责前台,B负责后台,B写了两个类:X与Y,A负责调用,那么1.A怎么知道B写了X与Y两个类呢?2.B又增加了Z 类怎么办,3.A在代码里写了n个X x = new X(), B把X类改名或重写了怎么办.为了解决这些困难,就提出了简单工厂模式,说白了,有一个基类或接口,然后n个类从它继承,再写一个类作为工厂,里面有个静 态方法负责根据转入参数的不同返回从基类或接口继承的具体对象:
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
{
string GetName();
}
public class Kernel : IPerson
{
public string GetName()
{
return "Kernel";
}
}
public class Json : IPerson
{
public string GetName()
{
return "Json";
}
}
public class PersonFactory
{
public static IPerson CreateInstance(string name)
{
string path = ConfigurationManager.AppSettings["AssemblyName"];
string className = "";
switch (name)
{
case "kernel":
className = ConfigurationManager.AppSettings["kernelClass"];
break;
default:
className = ConfigurationManager.AppSettings["JsonClass"];
break;
}
return Assembly.Load(path).CreateInstance(className) as IPerson;
}
}
static void Main(string[] args)
{
IPerson p1 = PersonFactory.CreateInstance("kernel");
Console.WriteLine(p1.GetName());
IPerson p2 = PersonFactory.CreateInstance("Json");
Console.WriteLine(p2.GetName());
Console.ReadKey();
}
如果有变更,现在就只需要更改工厂类就可以了,这样就在一定程度上必免了因为调用对象的变更而导致代码的重写
2.工厂方法模式
类不多时一般用简单工厂.如果类非常多,你就会发现这个工厂会奇大无比,这时就需要对这个工厂分解,工厂方法模式就这样提出来了.
工厂方法模式个人认为本质上就是对工厂也工厂了一遍.先用工厂产生特定类的工厂,然后用特定类的工厂生成你所需要的具体对象.
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
{
string GetName();
}
public class Kernel : IPerson
{
public string GetName()
{
return "Kernel";
}
}
public class Json : IPerson
{
public string GetName()
{
return "Json";
}
}
public interface ICreatePerson
{
IPerson CreateInstance();
}
public class CreateKernelFactory : ICreatePerson
{
public IPerson CreateInstance()
{
string path = ConfigurationManager.AppSettings["AssemblyName"];
string className = ConfigurationManager.AppSettings["kernelClass"];
return Assembly.Load(path).CreateInstance(className) as IPerson;
}
}
public class CreateJsonFactory : ICreatePerson
{
public IPerson CreateInstance()
{
string path = ConfigurationManager.AppSettings["AssemblyName"];
string className = ConfigurationManager.AppSettings["jsonClass"];
return Assembly.Load(path).CreateInstance(className) as IPerson;
}
}
static void Main(string[] args)
{
ICreatePerson c1 = new CreateKernelFactory();
IPerson p1 = c1.CreateInstance();
ICreatePerson c2 = new CreateJsonFactory();
IPerson p2 = c2.CreateInstance();
Console.WriteLine(p1.GetName());
Console.WriteLine(p2.GetName());
Console.ReadKey();
}
3.策略模式
有时候你会发现有些需求其实大体都是一样的,同一类的,就是计算方式不同,这时就可以用策略模式:
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
{
string GetCharge();
}
public class CashBuy : IBuy
{
double charge;
double cut;
public CashBuy(double charge, double cut)
{
this.charge = charge;
this.cut = cut;
}
public string GetCharge()
{
return (charge - cut).ToString();
}
}
public class CreditBuy : IBuy
{
double charge;
double precent;
public CreditBuy(double charge, double precent)
{
this.charge = charge;
this.precent = precent;
}
public string GetCharge()
{
return (charge * precent).ToString();
}
}
public class Context
{
IBuy buy;
public Context(IBuy buy)
{
this.buy = buy;
}
public string GetCharge()
{
return buy.GetCharge();
}
}
static void Main(string[] args)
{
Context c1 = new Context(new CashBuy(200, 40));
Context c2 = new Context(new CreditBuy(200, 7));
Console.WriteLine(c1.GetCharge());
Console.WriteLine(c2.GetCharge());
Console.ReadKey();
}
你会发现在这里不再用接口new出一个个具体对象,而统一用Context对象,并通过Context得到结果.其实这通过工厂模式也可以得到相同 的结果,但它们的测重点有所不同.举个例子:排序算法,我需要的是选择一种算法但这种算法是一种策略,而这些算法实际上是可以相互替代的,即快速排序,基 数排序都可实现问题,而我只要求选择一种.而不是工厂里面创建那样,创建产品A(他是根据要求,而不是选择,即只能创建A),他与产品B是不能互相替代 的。
然而纯粹的策略模式需要A知道B具体构造了哪些对象,会出现在谈简单工厂时所出的那些问题,所以,我们常常把简单工厂与策略模式一起使用:
4.简单工厂+策略模式
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
{
Cash,
Credit
}
public interface IBuy
{
double GetPrice();
}
public class CashBuy : IBuy
{
double price;
double cut;
public CashBuy(double price, double cut)
{
this.price = price;
this.cut = cut;
}
public double GetPrice()
{
return price - cut;
}
}
public class CreditBuy : IBuy
{
double price;
double precent;
public CreditBuy(double price, double precent)
{
this.precent = precent;
this.price = price;
}
public double GetPrice()
{
return price * (1 - precent);
}
}
public class Content
{
IBuy buy = null;
public Content(BuyType buyType, double price, double cut)
{
string path = ConfigurationManager.AppSettings["SimpeFactoryAndStrategyAssemble"];
string className = "";
switch (buyType)
{
case BuyType.Cash:
className = ConfigurationManager.AppSettings["cash"];
break;
default:
className = ConfigurationManager.AppSettings["credit"];
break;
}
//buy = Assembly.Load(path).CreateInstance(className, false, BindingFlags.Default, null, new object[] { price, cut }, null, null) as IBuy;
Type type = Type.GetType(className, true);
buy = Activator.CreateInstance(type, price, cut) as IBuy;
}
public double GetPrice()
{
return buy.GetPrice();
}
}
static void Main(string[] args)
{
Content c1 = new Content(BuyType.Cash, 200, 40);
Content c2 = new Content(BuyType.Credit, 200, 0.7);
Console.WriteLine(c1.GetPrice().ToString());
Console.WriteLine(c2.GetPrice().ToString());
Console.ReadKey();
}
Demo下载:
http://ljzforever.qupan.com/?folder=951925
参考的文章:
简单工厂模式 & 策略模式——《大话设计模式》读书笔记1
http://hi.baidu.com/springlie/blog/item/6052ad010f26670e1c958366.html
单一职责原则和 & 开放-封闭原则——《大话设计模式》读书笔记2
http://hi.baidu.com/springlie/blog/item/4d01d5c878efc01f7e3e6f59.html
策略模式和抽象工厂模式差别在那里??我怎么感觉两个一个样!!为了区分而区分???
http://topic.csdn.net/t/20050108/17/3709567.html
深入浅出工厂模式
http://blog.csdn.net/ai92/archive/2004/12/26/229825.aspx
深入浅出策略模式
http://blog.csdn.net/ai92/archive/2004/12/26/229825.aspx
简单工厂模式 和 策略模式 学习笔记
http://www.cnblogs.com/sun11086/archive/2009/02/06/1385510.html
简单工厂模式与工厂方法模式
http://hi.baidu.com/wookoo/blog/item/b49f1ac7f89d87ded1006097.html
策略模式和工厂模式的不同
http://www.cnblogs.com/ac1985482/archive/2009/03/07/1405608.html