设计模式---简单工厂

简单工厂模式：就是店---很多糕点，你需要通过工厂来生成。目的是为了减少代码，先写一个父类，然后让子类继承这个父类，然后在写一个工厂类，根据switch来调用不同的子类。

测试的时候，直接调用工厂类即可。

直接上代码：

下面的算法是一个 计算器的实现：

1. using System;
2. using System.Collections.Generic;
3. using System.Linq;
4. using System.Text;
5.  
6. namespace DesignDemo
7. {
8.     class Operation2
9.     {
10.         private double _numberA;
11.         private double _numberB;
12.  
13.         public double numberA
14.         {
15.             get {return _numberA;}
16.             set { _numberA = value; }
17.         }
18.  
19.         public double numberB
20.         {
21.             get { return _numberB; }
22.             set { _numberB = value; }
23.         }
24.  
25.         public virtual double GetResult()
26.         {
27.             double result = 0d;
28.             return result;
29.         }
30.     }
31.  
32.     class OperationAdd : Operation2
33.     {
34.         public override double GetResult()
35.         {
36.             double result = 0;
37.             result = numberA + numberB;
38.             return result;
39.         }
40.     }
41.  
42.     class OperationSub : Operation2
43.     {
44.         public override double GetResult()
45.         {
46.             double result = 0;
47.             result = numberA - numberB;
48.             return result;
49.         }
50.     }
51.  
52.     class OperationMul : Operation2
53.     {
54.         public override double GetResult()
55.         {
56.             double result = 0;
57.             result = numberA * numberB;
58.             return result;
59.         }
60.     }
61.  
62.     class OperationDiv : Operation2
63.     {
64.         public override double GetResult()
65.         {
66.             double result = 0;
67.             if (numberB == 0)
68.             {
69.                 throw new Exception("除数不能为0");
70.             }
71.             result = numberA / numberB;
72.             return result;
73.         }
74.     }
75.  
76.  
77.     /************************************************************************/
78.     /* 建立简单工厂模式：减少耦合，把变化的东西封装成类 */
79.     /************************************************************************/
80.  
81.     class OperationFactory
82.     {
83.         public static Operation2 createOperate(string operate)
84.         {
85.             Operation2 per = null;
86.             switch (operate)
87.             {
88.                 case "+":
89.                     per = new OperationAdd();
90.                     break;
91.                 case "-":
92.                     per = new OperationSub();
93.                     break;
94.                 case "*":
95.                     per = new OperationMul();
96.                     break;
97.                 case "/":
98.                     per = new OperationDiv();
99.                     break;
100.             }
101.             return per;
102.         }
103.     }
104. }