代碼無錯就是優？ 簡單工廠模式

1.1 面試受挫

1.2 初學者代碼毛病

1.3 代碼規范

1.4 面向對象編程

1.5 活字印刷 面向對象

喝酒唱歌+人生真爽，對酒當歌+人生真爽，對酒當歌+人生幾何，

可維護，可復用，可擴展，靈活性好，

1.6 面向對象好處

通過封裝，繼承，多態把程序的耦合度降低，

設計模式使程序更加靈活，容易修改且易於復用，

1.7 復制VS服用

計算與顯示分開，

1.8 業務的封裝

1.9 緊耦合VS松耦合

1.10 簡單工廠模式

運算類：

namespace OperationLibrary
{
    /// <summary>
    /// 運算類
    /// </summary>
    public class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;

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

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

        /// <summary>
        /// 得到運算結果
        /// </summary>
        /// <returns></returns>
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }

        /// <summary>
        /// 檢查輸入字符串是否准確
        /// </summary>
        /// <param name="currentNumber"></param>
        /// <param name="inputString"></param>
        /// <returns></returns>
        public static string checkNumberInput(string currentNumber, string inputString)
        {
            string result = "";
            if (inputString == ".")
            {
                if (currentNumber.IndexOf(".") < 0)
                {
                    if (currentNumber.Length == 0)
                        result = "0" + inputString;
                    else
                        result = currentNumber + inputString;
                }
            }
            else if (currentNumber == "0")
            {
                result = inputString;
            }
            else
            {
                result = currentNumber + inputString;
            }
            return result;
        }
    }

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

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

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

    /// <summary>
    /// 除法類
    /// </summary>
    class OperationDiv : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            if (NumberB == 0)
                throw new Exception("除數不能為0。");
            result = NumberA / NumberB;
            return result;
        }
    }

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

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

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

    /// <summary>
    /// 運算類工廠
    /// </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;
        }
    }

}

控制台：

namespace 計算器控制台
{

    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Console.Write("請輸入數字A：");
                string strNumberA = Console.ReadLine();
                Console.Write("請選擇運算符號(+、-、*、/)：");
                string strOperate = Console.ReadLine();
                Console.Write("請輸入數字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("結果是：" + strResult);
                Console.ReadLine();
            }
            catch (Exception ex)
            {
                Console.WriteLine("您的輸入有錯：" + ex.Message);
            }
        }

    }
}

WinForm：

namespace 計算器
{
    public partial class Form1 : Form
    {
        bool bOperate = false;
        Operation oper;

        public Form1()
        {
            InitializeComponent();
        }

        private void button0_Click(object sender, EventArgs e)
        {
            if (bOperate)
            {
                txtShow.Text = "";
                bOperate = false;
            }
            string number = ((Button)sender).Text;
            txtShow.Text = Operation.checkNumberInput(txtShow.Text, number);
        }

        private void buttonClear_Click(object sender, EventArgs e)
        {
            txtShow.Text = "";
        }

        private void buttonAdd_Click(object sender, EventArgs e)
        {
            if (txtShow.Text != "")
            {
                oper = OperationFactory.createOperate(((Button)sender).Text);
                oper.NumberA = Convert.ToDouble(txtShow.Text);
                bOperate = true;
            }
        }

        private void buttonEqual_Click(object sender, EventArgs e)
        {
            if (txtShow.Text != "")
            {
                if (((Button)sender).Text != "=")
                    oper = OperationFactory.createOperate(((Button)sender).Text);
                oper.NumberB = Convert.ToDouble(txtShow.Text);
                txtShow.Text = oper.GetResult().ToString();
                bOperate = true;
            }
        }

    }
}

1.11 UML類圖