设计模式-策略模式
先使用简单工厂设计一个商场收银软件
现金收费抽象类
abstract class CashSuper
{public abstract double acceptCash(double money);//现金收取超类的抽象方法，收取现金，参数为原价，返回为当前价
}
正常收费子类
class CashNormal:CashSuper
{public override double acceptCash(double money){return money;}
}
打折收费子类
class CashRebate:CashSuper
{private double moneyRebate = 1d;public CashRebate(string moneyRebate){this.moneyRebate = double.Parse(moneyRebate); }public override double acceptCash(double money){return money*moneyRebate;}
}
返利收费子类
class CashReturn:CashSuper
{private double moneyCondition = 0.0d;private double moneyReturn = 0.0d;public CashReturn(string moneyCondition,string moneyReturn){this.moneyCondition = double.Parse(moneyCondition);this.moneyReturn = double.Parse(moneyReturn);}public override double acceptCash(double money){double result = money;if(money >= moneyCondition)result = money - Math.Floor(money/moneyCondition) * moneyReturn;return result}
}
现金收费工厂类
class CashFactory{public static CashSuper createCashAccept(string type){CashSuper cs = null;switch(type){case "正常收费"；cs = new CashNormal();break;case "满300返100"；cs = new CashReturn("300","100");break; case "打8折"；cs = new CashRebate("0.8");break; }return cs;}
}
客户端窗体程序(主要部分)
double total = 0.0d;
private void btnOK_Click(object sender,EventArgs e){CashSuper csuper = CashFactory.createCashAccept(cbxType.SelectedItem.ToString());//要收的费用超类体现了多态double totalPrices = 0d;totalPrices = csuper.acceptCash(Convert.ToDouble(txtPrice.Text)*Convert.ToDouble(txtNum.txt));//单价x数量是原价total = total + totalPrices;
}
简单工厂的缺点
增加 需要打5折或者满500送200的促销活动时候，需要在生成工厂添加两个条件。
增加 满100积分10点，需要加一个积分算法，构造方法有两个参数：条件和返点，让它继承CashSuper,再增加分支条件。
简单工厂模式虽然能解决这个问题，但这个模式只是解决对象的创建问题，而且由于工厂本身包括了所有的收费方式，商场是可能经常性地更改打折额度和返利额度，每次维护或扩展收费方式都要改动这个工厂，以致代码需要重新编译部署，所以用它不是最好地办法
策略模式
Strategy类，定义所有支持的算法的公共接口
//抽象算法类
abstract class Strategy
{//算法方法public abstract void AlgorithmInterface();
}
ConcreteStrategy,封装了具体的算法或行为，继承于Strategy
//具体算法A
class ConcreteStategyA:Strategy{//算法A实现方法public override void AlgorithmInterface(){Console.WriteLine("算法A实现")}
}
//具体算法B
class ConcreteStategyB:Strategy{//算法B实现方法public override void AlgorithmInterface(){Console.WriteLine("算法B实现")}
}
//具体算法C
class ConcreteStategyC:Strategy{//算法C实现方法public override void AlgorithmInterface(){Console.WriteLine("算法C实现")}
}
Context,用一个ConcreteStrategy 来配置，维护一个对Strategy对象的引用
//上下文
class Context
{Strategy strategy;public Context(Strategy strategy){this.strategy = strategy;}//上下文接口public void ContextInterface(){strategy.AlgorithmInterface();}
}
客户端代码
static void Main(string[] args){Context context;context = new Context(new ConcreteStrategyA());context.ContextInterface();context = new Context(new ConcreteStrategyB());context.ContextInterface();context = new Context(new ConcreteStrategyC());context.ContextInterface();
}
策略模式实现商场收银
CashContext类(与简单工厂结合)
class CashContext
{CashSuper cs = null;public CashContext(string type){switch(type){case "正常收费"；cs = new CashNormal();break;case "满300返100"；cs = new CashReturn("300","100");break; case "打8折"；cs = new CashRebate("0.8");break; } }public double GetResult(double money){return cs.acceptCash(money);}
}
客户端主要代码
double total = 0.0d;
private void btnOK_Click(object sender,EventArgs e){CashContext csuper = new CashContext(cbxType.SelectedItem.ToString());double totalPrices = 0d;totalPrices = csuper.GetResult(Convert.ToDouble(txtPrice.Text)*Convert.ToDouble(txtNum.txt));//单价x数量是原价total = total + totalPrices;
}
两种设计模式总结
//简单工厂模式的用法CashSuper csuper = CashFactory.createCashAccept(...);...=csuper.acceptCash(...);
//策略模式与简单工厂结合的用法
CashContext csuper = new Cashcontext(...);
...=csuper.GetResult(...);
简单工厂模式需要让客户端认识两个类，CashSuper和CashFactory，而策略模式与简单工厂结合的用法，客户端只需要认识一个类CashContext就可以，耦合更加降低！
