步步为营 .NET 代码重构学习笔记 九

一、Duplicate Observed Data（复制[被监视数据]）

动机（Motivation）

将该笔数据拷贝到一个domain object中。建立一个Observer模式，用以对domain object 和GUI object内的重复数据进行同步控制（sync）。

示例

步步为营 .NET 设计模式学习笔记 十二、Observer (观察者模式)

二、Change Unidirectional Association to Bidirectional（将单向关联改为双向）

动机（Motivation）

添加一个反指针，并使修改函数（modifiers）能够同时更新两条连接。

示例

01 public class Order
02 {
03     private Customer _customer;
04
05     public Customer NewCustomer
06     {
07         get { return _customer; }
08         set { _customer = value; }
09     }
10 }
11
12 public class Customer
13 {
14 }

改为

01 public class Order
02  {
03      public List<Customer> CustomerList = new List<Customer>();
04
05      public void AddCustomer(Customer arg)
06      {
07          arg.orderlist.Add(this);
08          CustomerList.Add(arg);
09      }
10
11      public void RemoveCustomer(Customer arg)
12      {
13          arg.orderlist.Remove(this);
14          CustomerList.Remove(arg);
15      }
16  }
17
18  public class Customer
19  {
20      public List<Order> orderlist = new List<Order>();
21      public void AddOrder(Order arg)
22      {
23          arg.CustomerList.Add(this);
24          orderlist.Add(arg);
25      }
26      public void RemoveOrder(Order arg)
27      {
28          arg.CustomerList.Remove(this);
29          orderlist.Remove(arg);
30      }
31  }

三、Change Bidirectional Association to Unidirectional（将双向改为单向）

动机（Motivation）

两个classes之间有双向关联，但其中一个class如今不再需要另一个class的特性。

示例

01 public class Order
02     {
03         public List<Customer> CustomerList = new List<Customer>();
04
05         public void AddCustomer(Customer arg)
06         {
07             arg.orderlist.Add(this);
08             CustomerList.Add(arg);
09         }
10
11         public void RemoveCustomer(Customer arg)
12         {
13             arg.orderlist.Remove(this);
14             CustomerList.Remove(arg);
15         }
16     }
17
18     public class Customer
19     {
20         public List<Order> orderlist = new List<Order>();
21         public void AddOrder(Order arg)
22         {
23             arg.CustomerList.Add(this);
24             orderlist.Add(arg);
25         }
26         public void RemoveOrder(Order arg)
27         {
28             arg.CustomerList.Remove(this);
29             orderlist.Remove(arg);
30         }
31     }

改为

01 public class Order
02 {
03     private Customer _customer;
04
05     public Customer NewCustomer
06     {
07         get { return _customer; }
08         set { _customer = value; }
09     }
10 }
11
12 public class Customer
13 {
14 }

四、Replace Magic Number with Symbolic Constant（以符号常量/字面常量取侙魔法数）

动机（Motivation）

创造一个常量，根据其意义为它命名，并将上述的字面数值替换为这个常量。

示例

1 public double PotentialEnergy(double mass, double height)
2 {
3     return mass * 9.51 * height;
4 }

改为

1 private double GRAVITATIONAL_CONSTANT = 9.51;
2 public double PotentialEnergy(double mass, double height)
3 {
4     return mass * GRAVITATIONAL_CONSTANT * height;
5 }

五、Encapsulate Field（封装值域）

动机（Motivation）

将它声明为private，并提供相应的访问函数（accessors）

示例

1 public string _name;

改为

1 private  string _name;
2
3 public string Name
4 {
5     get { return _name; }
6     set { _name = value; }
7 }

六、Replace Type Code with Class（以类取代型别码）

动机（Motivation）

以一个新的class替换该数值型别码（type code）

示例

01 public class Person
02 {
03     public  int O = 0;
04     public  int A = 1;
05     public  int B = 2;
06     public  int AB = 3;
07
08     private int _bloodGroup;
09
10     public Person(int bloodGroup)
11     {
12         _bloodGroup = bloodGroup;
13     }
14     public int NewBloodGroup
15     {
16         get { return _bloodGroup; }
17         set { _bloodGroup = value; }
18     }
19 }

改为

01	public class Person

02

{

03	public int O = BloodGroup.O.Code;

04	public int A = BloodGroup.A.Code;

05	public int B = BloodGroup.B.Code;

06	public int AB = BloodGroup.AB.Code;

07

08

09	private int _bloodGroup;

10

11	public Person(int bloodGroup)

12

{

13	_bloodGroup = bloodGroup;

14

}

15

16	public int NewBloodGroup

17

{

18	get { return _bloodGroup; }

19	set { _bloodGroup = value; }

20

}

21

}

22

23	public class BloodGroup

24

{

25	public static BloodGroup O = new BloodGroup(0);

26	public static BloodGroup A = new BloodGroup(1);

27	public static BloodGroup B = new BloodGroup(2);

28	public static BloodGroup AB = new BloodGroup(3);

29

30	private int _code;

31

32	private BloodGroup(int code)

33

{

34	_code = code;

35

}

36

37	public int Code

38

{

39	get { return _code; }

40	set { _code = value; }

41

}

42

43

}