面向对象下计算器的编码实现

1、封装

首先是新建一个运算类（Calcultor.cs），它包含两个属性strNumA和strNumB，用以储存计算时的两个数，此外，还有一个虚方法Getresult()，用以得到运算的结果。

public class calculator
{
/// <summary>
/// 定义运算类的属性
/// </summary>
private double dblNumA = 0,dblNumB=0;

/// <summary>
/// 定义属性dblNumA的操作方法
/// </summary>
public double dblnuma
{
get { return dblNumA; }
set { dblNumA = value; }
}

/// <summary>
/// 定义属性dblNumB的操作方法
/// </summary>
public double dblnumb
{
get { return dblNumB; }
set { dblNumB = value; }
}

/// <summary>
/// 得到运算结果
/// </summary>
/// <returns>dblresult</returns>
public virtual string GetResult()
{
string dblResult ="0";
return dblResult;
}
}

2、继承

然后将操作加、减、乘、除写成运算类的子类，继承运算类后重写Getresult()。

/// <summary>
/// 加法类
/// </summary>
class OperationAdd : calculator
{
public override string GetResult()
{
string dblresult = "0";
dblresult = (dblnuma + dblnumb).ToString();
return dblresult;
}
}
/// <summary>
/// 减法类
/// </summary>
class OperationSub : calculator
{
public override string GetResult()
{
string dblresult = "0";
dblresult = (dblnuma - dblnumb).ToString();
return dblresult;
}
}
/// <summary>
/// 乘法类
/// </summary>
class OperationMul : calculator
{
public override string GetResult()
{
string dblresult = "0";
dblresult = (dblnuma * dblnumb).ToString();
return dblresult;
}
}
/// <summary>
/// 除法类
/// </summary>
class OperationDiv : calculator
{
public override string GetResult()
{
string dblresult = "0";
if (dblnumb != 0)
{
dblresult = (dblnuma / dblnumb).ToString();
}
else
{
dblresult = "除数不能为0！";
}
return dblresult;
}
}

3、多态

再用一个单独的类创造实例的过程。

public class factory
{
public static calculator createOperation(string strOperation)
{
calculator cal = null;
switch (strOperation)
{
case "+":
{
cal = new OperationAdd();
break;
}
case "-":
{
cal = new OperationSub();
break;
}
case "*":
{
cal = new OperationMul();
break;
}
case "/":
{
cal = new OperationDiv();
break;
}
}
return cal;
}
}