【设计模式】 策略模式

  class Strategy
    {
        public static void Test()
        {
            double money = 600;
            DiscountBase discount = DiscountFactory.GetDiscount("打折");
            if (discount!=null)
            {
                double result = discount.GetResult(money);
            }
        }
    }

    internal class DiscountFactory
    {
        public static DiscountBase GetDiscount(string type)
        {
            switch (type)
            {
                case "原价":
                    return new NoDiscount();
                case "打折":
                    return new OffDiscount();
                case "满500减300":
                    return new MulDiscount();
                default:
                    return null;
            }
        }
    }

    internal abstract class DiscountBase
    {
        public abstract double GetResult(double a);
    }

    internal class NoDiscount : DiscountBase
    {
        public override double GetResult(double a)
        {
            return a;
        }
    }

    internal class OffDiscount : DiscountBase
    {
        public override double GetResult(double a)
        {
            return a * 0.8;
        }
    }

    internal class MulDiscount : DiscountBase
    {
        public override double GetResult(double a)
        {
            if (a > 500)
            {
                return a - 300;
            }
            return a;
        }
    }