设计模式-策略模式

Strategy Pattern

—抽象策略角色： 策略类，通常由一个接口或者抽象类实现。

—具体策略角色：包装了相关的算法和行为。

—环境角色：持有一个策略类的引用，最终给客户端调用

 

 //抽象算法类

    abstract class Strategy

    {

        //算法方法

        public abstract void AlgorithmInterface();

    }

  

 //具体算法A
    class ConcreteStrategyA : 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 ConcreteStrategyB : 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 ConcreteStrategyC : Strategy
    {
        //算法C实现方法
        public override void AlgorithmInterface()
        {
            Console.WriteLine("算法C实现");
        }
    }

 

 //上下文
    class Context
    {
        Strategy strategy;

        public Context(Strategy strategy)
        {
            this.strategy = strategy;
        }
        //上下文接口
        public void ContextInterface()
        {
            strategy.AlgorithmInterface();
        }
    }

 

客户端调用：

 Context context;

 context = new Context(new ConcreteStrategyA());
 context.ContextInterface();

 context = new Context(new ConcreteStrategyB());
 context.ContextInterface();

 context = new Context(new ConcreteStrategyC());
 context.ContextInterface();

 

 

学习示例： 

    abstract class CashSuper
    {
        public abstract double acceptCash(double money);
    }


    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;
        } 
    }


    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;
        } 
    }

    class CashNormal : CashSuper
    {
        public override double acceptCash(double money)
        {
            return money;
        } 
    }


 //收费策略Context
class CashContext
{
    //声明一个现金收费父类对象
    private CashSuper cs;

    //设置策略行为，参数为具体的现金收费子类（正常，打折或返利）
    public CashContext(CashSuper csuper)
    {
        this.cs = csuper;
    }

    //得到现金促销计算结果（利用了多态机制，不同的策略行为导致不同的结果）
    public double GetResult(double money)
    {
        return cs.acceptCash(money);
    }
}

客户端调用：

            CashContext cc = null;
            switch (cbxType.SelectedItem.ToString())
            {
                case "正常收费":
                    cc = new CashContext(new CashNormal());
                    break;
                case "满300返100":
                    cc = new CashContext(new CashReturn("300", "100"));
                    break;
                case "打8折":
                    cc = new CashContext(new CashRebate("0.8"));
                    break;
            }

            double totalPrices = 0d;
            totalPrices = cc.GetResult(Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text));

 

大话设计模式 -程杰