设计模式之策略模式的实现

策略模式通用UML类图 with StarUML

具体实现的UML类图 with StarUML

折扣接口

namespace StrategyPattern
{
     interface Discount
    {
        double Calculate(double price);
    }
}

学生折扣类

namespace StrategyPattern
{
    internal class StudentDiscount:Discount
    {
        private const double DISCOUNT = 0.8;
 
        public double Calculate(double price)
        {
            Console.WriteLine("学生票：");
            return price * DISCOUNT;
        }
    }
}

儿童折扣类

namespace StrategyPattern
{
    internal class ChildrenDiscount : Discount
    {
        private const double DISCOUNT = 10;
 
        public double Calculate(double price)
        {
            Console.WriteLine("儿童票：");
            return price - DISCOUNT;
        }
    }
}

VIP折扣类

namespace StrategyPattern
{
    internal class VIPDiscount : Discount
    {
        private const double DISCOUNT = 0.5;
        public double Calculate(double price)
        {
            Console.WriteLine("VIP票：");
            Console.WriteLine("增加积分！");
            return price * DISCOUNT;
        }
    }
}

电影票类

namespace StrategyPattern
{
    internal class MovieTicket
    {
        private double price;
        private Discount discount;
 
        public void SetDiscount(Discount discount)
        {
            this.discount = discount;
        }
        public double Price
        {
            get { return discount.Calculate(this.price); }
            set { price = value; }
        }
    }
}

XML配置文件

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<appSettings>
		<add key="discountType" value="StrategyPattern.ChildrenDiscount"/>
	</appSettings>
</configuration>

 

测试代码

namespace StrategyPattern
{
    internal class Program
    {
        static void Main(string[] args)
        {
            MovieTicket mt = new MovieTicket();
            double originalPrice = 60;
            double currentPrice;
 
            mt.Price = originalPrice;
            Console.WriteLine($"原始价为：{originalPrice}");
            Console.WriteLine("---------------------------------");
 
            Discount discount;
            string discountType = ConfigurationManager.AppSettings["discountType"];
            discount = (Discount)Assembly.Load("StrategyPattern").CreateInstance(discountType);
            mt.SetDiscount(discount);
 
            currentPrice = mt.Price;
            Console.WriteLine($"折后价为：{currentPrice}");
            Console.Read();
        }
    }
}

执行结果