设计模式-策略者模式

一、定义

    策略模式是针对一组算法，将每个算法封装到具有公共接口的独立的类中，从而使它们可以相互替换。策略模式使得算法可以在不影响到客户端的情况下发生变化。

 

二、UML类图

 

三、例子展示

namespace 策略者模式
{
    public interface ITaxStrategy
    {
        double GetTax(double money);
    }

    public class PersnalStrategy : ITaxStrategy
    {
        public double GetTax(double money)
        {
            return money * 0.1;
        }
    }

    public class EnterpriseTaxStrategy : ITaxStrategy
    {
        public double GetTax(double money)
        {
            return (money - 4000) > 0 ? (money - 4000) * 0.045 : 0.0;
        }
    }

    public class TaxContext
    {
        private ITaxStrategy _strategy;

        public TaxContext(ITaxStrategy taxStrategy)
        {
            _strategy = taxStrategy;
        }

        public double GetTax(double money)
        {
            return _strategy.GetTax(money);
        }
    }

    public class Client
    {
        public static void Process()
        {
            TaxContext taxContext = new TaxContext(new PersnalStrategy());
            double tax = taxContext.GetTax(10000);
            Console.WriteLine("个人所得税："+tax);

             taxContext = new TaxContext(new EnterpriseTaxStrategy());
             tax = taxContext.GetTax(100000);
            Console.WriteLine("企业所得税：" + tax);

            // 与简单工厂模式一起，避免客户端既依赖于TaxContext，又依赖于具体策略者。这样客户端只需要知道TaxContext就可以了
            TaxContext2 taxContext2 = new TaxContext2("PersnalStrategy");
            double tax2 = taxContext2.GetTax(10000);
            Console.WriteLine("升级版 个人所得税：" + tax2);

            taxContext2 = new TaxContext2("EnterpriseTaxStrategy");
            tax2 = taxContext2.GetTax(100000);
            Console.WriteLine("升级版 企业所得税：" + tax2);
        }
    }

    public class TaxContext2
    {
        private ITaxStrategy _strategy;

        /// <summary>
        /// 简单工厂一起
        /// </summary>
        /// <param name="taxType"></param>
        public TaxContext2(string taxType)
        {
            switch (taxType)
            {
                case "PersnalStrategy":
                    _strategy = new PersnalStrategy();
                    break;
                case "EnterpriseTaxStrategy":
                    _strategy = new EnterpriseTaxStrategy();
                    break;
                default:
                    break;
            }
        }

        public double GetTax(double money)
        {
            return _strategy.GetTax(money);
        }
    }
}

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