设计模式:(一)简单工厂
程序员文章站
2024-01-21 20:42:16
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问题:写一个计算器的控制台应用程序
功能要求:
(1)实现+、-、*、/四种基本运算;
(2)程序运行时,用户输入两个数和运算符号,即可得到运算结果。
public class Operation //运算基类
{
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() //定义虚方法
{
double result = 0.0;
return result;
}
}
class OperationAdd : Operation //加法类,继承Operation
{
public override double GetResult() //重写虚方法
{
double result = 0.0;
result = NumberA + NumberB;
return result;
}
}
class OperationSub : Operation //减法类,继承Operation
{
public override double GetResult() //重写虚方法
{
double result = 0.0;
result = NumberA - NumberB;
return result;
}
}
class OperationMul : Operation //乘法类,继承Operation
{
public override double GetResult() //重写虚方法
{
double result = 0.0;
result = NumberA * NumberB;
return result;
}
}
class OperationDiv : Operation //除法类,继承Operation
{
public override double GetResult() //重写虚方法
{
double result = 0.0;
if (NumberB == 0)
throw new Exception("除数不能为0。");
result = NumberA / NumberB;
return result;
}
}
public class OperationFactory //工厂类
{
public static Operation createOperate(string operate) //工厂方法
{
Operation oper = null; //声明基类型变量
switch (operate) //根据传进来的运算符参数决定生成哪个子类对象
{
case "+":
oper = new OperationAdd(); //创建加法类
break;
case "-":
oper = new OperationSub(); //创建减法类
break;
case "*":
oper = new OperationMul(); //创建乘法类
break;
case "/":
oper = new OperationDiv(); //创建除法类
break;
}
return oper;
}
}
class Program
{
static void Main(string[] args)
{
try
{
Console.Write("请输入数字A: ");
string strNumberA = Console.ReadLine(); //接受屏幕输入的数值1
Console.Write("请选择运算符号(+、-、*、/): ");
string strOperate = Console.ReadLine(); //用户选择运算符号
Console.Write("请输入数字B: ");
string strNumberB = Console.ReadLine(); //接受屏幕输入的数值2
double strResult = 0.0;
Operation oper; //声明基类型变量
oper = OperationFactory.createOperate(strOperate); //根据用户的输入创建子运算类
oper.NumberA = Convert.ToDouble(strNumberA);
oper.NumberB = Convert.ToDouble(strNumberB);
strResult = oper.GetResult(); //多态,调用子类的方法
Console.WriteLine("结果是 " + strResult);
Console.ReadLine();
}
catch (Exception ex)
{
Console.WriteLine("输入有错", ex.Message);
Console.ReadLine();
}
}
}
参考书籍:大话设计模式-程杰