【设计模式】简单工厂模式-学习

任何类的设计都要遵循耦合性低，避免重复。

 

设计模式的目的主要有3易。让项目易维护，易扩展，易复用。

 

易维护： 修改某个功能，只要修改最少的部分，比如某个类的方法。

易扩展： 项目本来有加减乘除功能，现在要扩展 根号，取余功能。  要尽量的少改代码。

易复用： 要让设计的方法不管在 控制台应用程序，web应用程序 还是 Winform程序都能使用。

 

 

 

 

 

 

简单工厂模式：解决了对象的创建问题

 

 

Operator.cs 定义了几个类，实现了加减功能。    其中通过OpeartorFactor 根据操作符来实例相应的对象。

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace 简单工厂模式

{

    class Operation

    {

        private double _numberA = 0.0;

        private double _numberB = 0.0;

        public double NumberA

        {

            get { return _numberA; }

            set { _numberA = value; }

        }

        public double NumberB

        {

            get { return _numberB; }

            set { _numberB = value; }

        }

        public virtual double getResult()

        {

            double result = 0.0;

            return result;

        }

    }

    class OpeartionAdd : Operation

    {

        public override double getResult()

        {

            double result = 0.0;

            result = NumberA + NumberB;

            return result;

        }

    }

    class OpeartionDel : Operation

    {

        public override double getResult()

        {

            double result = 0.0;

            result = NumberA - NumberB;

            return result;

        }

    }

    class OperationFactory

    {

        public static Operation createOpeartion(string operate)

        {

            Operation oper = null;

            switch (operate)

            {

                case "+":

                    oper = new OpeartionAdd();

                    break;

                case "-":

                    oper = new OpeartionDel();

                    break;

            }

            return oper;

        }

    }

}

 

 

现在想加入 乘除功能，那怎么办呢？

只要 先添加 2个类，并重写getResult()方法，然后再 工厂类中 加入  符号的判断

class  OpeartionMul:Operation    

class  OpeartionDiv:Operation 

 

case "*":

          oper = new OpeartionMul();

          break;

修改后的文件

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace 简单工厂模式

{

    class Operation

    {

        private double _numberA = 0.0;

        private double _numberB = 0.0;

        public double NumberA

        {

            get { return _numberA; }

            set { _numberA = value; }

        }

        public double NumberB

        {

            get { return _numberB; }

            set { _numberB = value; }

        }

        public virtual double getResult()

        {

            double result = 0.0;

            return result;

        }

    }

    class OpeartionAdd : Operation

    {

        public override double getResult()

        {

            double result = 0.0;

            result = NumberA + NumberB;

            return result;

        }

    }

    class OpeartionDel : Operation

    {

        public override double getResult()

        {

            double result = 0.0;

            result = NumberA - NumberB;

            return result;

        }

    }

    class OpeartionMul : Operation

    {

        public override double getResult()

        {

            double result = 0.0;

            result = NumberA * NumberB;

            return result;

        }

    }

    class OpeartionDiv : Operation

    {

        public override double getResult()

        {

            double result = 0.0;

            result = NumberA / NumberB;

            return result;

        }

    }

    class OperationFactory

    {

        public static Operation createOpeartion(string operate)

        {

            Operation oper = null;

            switch (operate)

            {

                case "+":

                    oper = new OpeartionAdd();

                    break;

                case "-":

                    oper = new OpeartionDel();

                    break;

                case "*":

                    oper = new OpeartionMul();

                    break;

                case "/":

                    oper = new OpeartionDiv();

                    break;

            }

            return oper;

        }

    }

}