设计模式之简单工厂模式

简单工厂模式实现计算器功能:

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

namespace 简单工厂模式
{
    class Program
    {
        static void Main(string[] args)
        {

            Operation operation = OperationFactory.CreateOperation("/");
            operation.param1 = 4;
            operation.param2 = 0;
            Console.WriteLine(operation.GetResult());
            Console.ReadKey();
        }

        /// <summary>
        /// 操作类的父类
        /// </summary>
        public abstract class Operation
        {
            public double param1 { get; set; }
            public double param2 { get; set; }

            public abstract  double GetResult();
          
        }

        /// <summary>
        /// 加法类
        /// </summary>
        public class AddOperation:Operation
        {
            public override double GetResult()
            {
                return param1 + param2;
            }
        }
        /// <summary>
        /// 减法类
        /// </summary>
        public class MinusOperation:Operation
        {
            public override double GetResult()
            {
                return param1 - param2;
            }
        }
        /// <summary>
        /// 乘法类
        /// </summary>
        public class MulOperation:Operation
        {
            public override double GetResult()
            {
                return param1 * param2;
            }
        }
        /// <summary>
        /// 除法类
        /// </summary>
        public class DelOperation:Operation
        {
            public override double GetResult()
            {
               if(param2==0)
               {
                   throw new Exception("除数不能为0");
               }
               return param1 / param2;
            }
        }

        /// <summary>
        /// 工厂类，管理所有的操作,并且向外提供访问的方法
        /// </summary>
        public class OperationFactory
        {
            /// <summary>
            /// 根据用户提供的操作符去创建对应的类
            /// </summary>
            /// <param name="operationName"></param>
            /// <returns></returns>
            public static Operation CreateOperation(string operationName)
            {
                Operation operation = null;
                switch(operationName)
                {
                    case "+":
                        operation = new AddOperation();
                        break;
                    case "-":
                        operation = new MinusOperation();
                        break;
                    case "*":
                        operation = new MulOperation();
                        break;
                    case "/":
                        operation = new DelOperation();
                        break;
                }
                return operation;
            }
        }
    }
}

 要点：简单工厂模式只是解决了创建对象的问题，而且工厂本身是不轻易修改的。2