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1、设计模式(Design Pattern),张凯 副教授计算机学院 软件工程系,问题(Problem),实现控制台计算器利用任意一种面向对象的语言要求输入2个数和运算符，得到结果,问题(Problem),static void Main(string args) 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
2、strNumberB = Console.ReadLine(); string strResult = ; switch (strOperate) case +: strResult = (double.Parse(strNumberA) + double.Parse(strNumberB).ToString(); break; case -: strResult = (double.Parse(strNumberA) - double.Parse(strNumberB).ToString(); break; case *: strResult = (double.Parse(strNumbe
3、rA) * double.Parse(strNumberB).ToString(); break; case /: if (strNumberB != 0) strResult = (double.Parse(strNumberA) / double.Parse(strNumberB).ToString(); else strResult = 除数不能为0; break; Console.WriteLine(结果是： + strResult); Console.ReadLine(); ,问题(Problem),原来的代码可复用吗？,问题(Problem),实现计算器Ctrl+C 和 Ctrl+
4、V维护的时候，带来灾难尽可能的办法去避免重复通过面向对象设计，让数据计算和用户交互方式分开,问题(Problem),class Operation public static double GetResult(double numberA, double numberB, string operate) double result = 0; switch (operate) case +: result = numberA + numberB; break; case -: result = numberA - numberB; break; case *: result = numberA
5、* numberB; break; case /: result = numberA / numberB; break; return result; ,问题(Problem),问题(Problem),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：); str
6、ing strNumberB = Console.ReadLine(); string strResult = ; strResult = Operation.GetResult(double.Parse(strNumberA), double.Parse(strNumberB), strOperate).ToString(); Console.WriteLine(结果是： + strResult); Console.ReadLine(); catch (Exception ex) Console.WriteLine(您的输入有错： + ex.Message); ,问题(Problem),pr
7、ivate void button8_Click(object sender, EventArgs e) if (bOperate) textBox1.Text = ; bOperate = false; textBox1.Text = textBox1.Text + (Button)sender).Text; private void button14_Click(object sender, EventArgs e) if (textBox1.Text != ) operate = (Button)sender).Text; numberA = double.Parse(textBox1.
8、Text); bOperate = true; private void button17_Click(object sender, EventArgs e) if (textBox1.Text != ) numberB = double.Parse(textBox1.Text); textBox1.Text = Operation.GetResult(numberA, numberB, operate).ToString(); bOperate = true; ,bool bOperate = false;double numberA = 0;double numberB = 0;strin
9、g operate = ;,问题(Problem),这种改变很有效，体现了面向对象的重要原则之一,单一职责原则,问题(Problem),添加平方根运算,问题(Problem),class Operation public static double GetResult(double numberA, double numberB, string operate) double result = 0; switch (operate) case +: result = numberA + numberB; break; case -: result = numberA - numberB; br
10、eak; case *: result = numberA * numberB; break; case /: result = numberA / numberB; break; return result; ,问题(Problem),紧耦合 vs 松耦合Switch中添加一个分支，搞定！思考：运算 + - * / 的代码GetResult是正确的，却需要在修改的时候暴露？如何修改或添加新运算，不影响其它的运算代码？,违背面向对象设计原则：开放封闭原则,问题(Problem),class Operation public static double GetResult(double numberA, double numberB, string operate) double result = 0; switch (operate) case +: result = numberA + numberB; break; case -: result = numberA - numberB; break; case *: result = numberA * numberB; break; case /: result = numberA / numberB; break; return result; ,
