设计模式-策略模式C#版

设计模式-策略模式C#版

策略模式是一种常见和常用的设计模式，策略的独立和抽象。

常见的场景就是电子商务中的打折策略。可以随着用户类型的不同，打折的策略也不同。

或者是游戏中打怪场景，怪的掉血策略，随着自己的级别，装备不同，怪的掉血不同。

今天的列子是打折策略，根据用户类型不同，打折策略不同。

需要在金额上做不同的打折策略，所以就在金额上留下一个口子，一个接口，传入不同的策略实现，每种实现都针对金额打不同的折扣。

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DomainModel.Model
{
    ///
    /// 打折策略
    ///
    public interface IDiscountStrategy
    {
        decimal Apply(decimal originalPrice);
    }

    public class Price
    {
        private IDiscountStrategy _discountStrategy;
        private decimal _salePrice;

        public Price(decimal salePrice, IDiscountStrategy discountStrategy)
        {
            this._salePrice = salePrice;
            this._discountStrategy = discountStrategy;
        }
        ///
        /// 应用策略
        ///
        ///
        public void SetDiscountStrategy(IDiscountStrategy discountStrategy)
        {
            this._discountStrategy = discountStrategy;
        }
        ///
        /// 返回打折后的价格
        ///
        public decimal SalePrice
        {

            get
            {
                return this._discountStrategy.Apply(this._salePrice);
            }
        }

    }

    public class Product
    {

        public int Id { get; set; }

        public string Name { get; set; }

        public Price Price { get; set; }
    }
    public enum CustomerType
    {
        ///
        ///  不打折
        ///
        General = 0,
        ///
        ///  6折
        ///
        Trade = 1
    }
    public class NullDiscountStrategy : IDiscountStrategy
    {

        public decimal Apply(decimal originalPrice)
        {
            return originalPrice;
        }
    }
    public class TradeDiscountStrategy : IDiscountStrategy
    {
        public decimal Apply(decimal originalPrice)
        {
            return originalPrice * 0.6m;
        }
    }
    ///
    /// 折扣策略工厂
    ///
    public sealed class DiscountStrategyFactory
    {

        public static IDiscountStrategy GetDiscountStrategy(CustomerType customerType)
        {
            switch (customerType)
            {
                case CustomerType.General:
                    return new NullDiscountStrategy();
                default:
                    return new TradeDiscountStrategy();
            }
        }
    }
    public interface IProductRepository
    {
        IList Find();
    }

    public static class ProductListExtensions
    {
        public static void ApplyDiscount(this IList products, IDiscountStrategy discountStrategy)
        {
            foreach (var p in products)
            {
                p.Price.SetDiscountStrategy(discountStrategy);
            }
        }
    }

    public class ProductRepository:IProductRepository
    {
        public IList Find()
        {
            return new List();
        }
    }
    public class ProductService
    {
        private IProductRepository _productRepository;
        public ProductService()
        {
            this._productRepository = new ProductRepository();
        }
        public ProductService(IProductRepository productRepository)
        {
            this._productRepository = productRepository;
        }

        public IList Find(CustomerType customerType)
        {
            var discountStrategy = DiscountStrategyFactory.GetDiscountStrategy(customerType);
            var products = this._productRepository.Find();
            products.ApplyDiscount(discountStrategy);
            return products;
        }
    }

    public class Client
    {
        private CustomerType _customerType = CustomerType.Trade;

        public void FindProducts()
        {
            var service = new ProductService();
            var products = service.Find(this._customerType);
        }
    }
}

 

 

参考文献

1.走向.NET架构设计—第三章—分层设计，初涉架构(中篇)