简单工厂模式

基本简介

从设计模式的类型上来说，简单工厂模式是属于创建型模式，又叫做静态工厂方法（Static Factory Method）模式，但不属于23种GOF设计模式之一。简单工厂模式是由一个工厂对象决定创建出哪一种产品类的实例。简单工厂模式是工厂模式家族中最简单实用的模式，可以理解为是不同工厂模式的一个特殊实现。
实现方式
简单工厂模式的实质是由一个工厂类根据传入的参数，动态决定应该创建哪一个产品类（这些产品类继承自一个父类或接口）的实例。
简单工厂模式的UML类图:
View Code

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

namespace OperationLibrary
{
class Program
{
static void Main(string[] args)
{
try
{
Console.Write("请输入数字A：");
string strNumberA = Console.ReadLine();
Console.Write("请选择运算符号(+、-、*、/)：");
string strOperate = Console.ReadLine();
Console.Write("请输入数字B：");
string strNumberB = Console.ReadLine();
string strResult = "";

Operation oper;
oper = OperationFactory.createOperate(strOperate);
oper.NumberA = Convert.ToDouble(strNumberA);
oper.NumberB = Convert.ToDouble(strNumberB);
strResult = oper.GetResult().ToString();

Console.WriteLine("结果是：" + strResult);

Console.ReadLine();
}
catch (Exception ex)
{
Console.WriteLine("您的输入有错：" + ex.Message);
}
}
}

/// <summary>
/// 运算类
/// </summary>
public class Operation
{
private double _numberA = 0;
private double _numberB = 0;

/// <summary>
/// 数字A
/// </summary>
public double NumberA
{
get
{
return _numberA;
}
set
{
_numberA = value;
}
}

/// <summary>
/// 数字B
/// </summary>
public double NumberB
{
get
{
return _numberB;
}
set
{
_numberB = value;
}
}

/// <summary>
/// 得到运算结果
/// </summary>
/// <returns></returns>
public virtual double GetResult()
{
double result = 0;
return result;
}
}

/// <summary>
/// 加法类
/// </summary>
class OperationAdd : Operation
{
public override double GetResult()
{
double result = 0;
result = NumberA + NumberB;
return result;
}
}

/// <summary>
/// 减法类
/// </summary>
class OperationSub : Operation
{
public override double GetResult()
{
double result = 0;
result = NumberA - NumberB;
return result;
}
}

/// <summary>
/// 乘法类
/// </summary>
class OperationMul : Operation
{
public override double GetResult()
{
double result = 0;
result = NumberA * NumberB;
return result;
}
}

/// <summary>
/// 除法类
/// </summary>
class OperationDiv : Operation
{
public override double GetResult()
{
double result = 0;
if (NumberB == 0)
throw new Exception("除数不能为0。");
result = NumberA / NumberB;
return result;
}
}

/// <summary>
/// 运算类工厂
/// </summary>
public class OperationFactory
{
public static Operation createOperate(string operate)
{
Operation oper = null;
switch (operate)
{
case "+":
{
oper = new OperationAdd();
break;
}
case "-":
{
oper = new OperationSub();
break;
}
case "*":
{
oper = new OperationMul();
break;
}
case "/":
{
oper = new OperationDiv();
break;
}
}

return oper;
}
}
}