学步园

实现一个简单的计算器：

1.定义一个运算类，该类应该有2个操作数属性；一个结果方法，考虑到不同运算情况下运算结果不一样，所以此处用抽象方法，子类方便去重写；当然，还需要一个对输入数字的检查方法

/// <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>
        /// <remarks>抽象方法，可重写</remarks>
        /// <returns></returns>
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }

        /// <summary>
        /// 检查输入的字符串是否准确
        /// </summary>
        /// <param name="currentNumber">当前数字</param>
        /// <param name="inputString">输入的数字</param>
        /// <returns></returns>
        public static string checkNumberInput(string currentNumber, string inputString)
        {
            string result = "";
            if (inputString == ".")
            {
                if (currentNumber.IndexOf(".") < 0)//没有小数位
                {
                    if (currentNumber.Length == 0)//当前数字是空
                        result = "0.";
                    else
                        result = currentNumber + ".";//不为空就加一个小数点
                }
            }
            else if (currentNumber == "0") //当前数字是0
            {
                result = inputString;
            }
            else
            {
                result = currentNumber + inputString;
            }

            return result;
        }
    }

2.实现各种运算方法

/// <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>
    /// 平方类
    /// </summary>
    class OperationSqr : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberB * NumberB;
            return result;
        }
    }

    /// <summary>
    /// 平方根类
    /// </summary>
    class OperationSqrt : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            if (NumberB < 0)
                throw new Exception("。");
            result = Math.Sqrt(NumberB);
            return result;
        }
    }

    /// <summary>
    /// 相反数类
    /// </summary>
    class OperationReverse : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = -NumberB;
            return result;
        }
    }

3.下面我们来实现加工厂的处理

通过传进不同的运算符得到不同对象模板，然后进行对应的模板方法运算

/// <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;
                    }
                case "sqr":
                    {
                        oper = new OperationSqr();
                        break;
                    }
                case "sqrt":
                    {
                        oper = new OperationSqrt();
                        break;
                    }
                case "+/-":
                    {
                        oper = new OperationReverse();
                        break;
                    }
            }

            return oper;
        }
    }

5.最后我们来控制台程序测试下;

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);
            }
        }