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  • 步步为营 .NET 代码重构学习笔记 十

    一、Replace Type Code with Subclasses （以子类取代型别码）

    动机（Motivation）

    以一个subclass取代这个type code，如果面对的type code不会影响宿主类的行为，可以使用Replace Type Code with Class 来处理它们。但如果type code 会影响宿主类的行为，那么最好的办法就是借助多态（polymorphism）业处理 变化行为。

    示例

    view sourceprint?
    01 public class Employee
    02 {
    03     private int _type;
    04     public static int ENGINEER = 0;
    05     public static int SALEMAN = 1;
    06     public static int MANAGER = 2;
    07  
    08     public Employee(int type)
    09     {
    10         _type = type;
    11     }
    12 }

    改为

    view sourceprint?
    01 public class Employee
    02 {
    03     private int _type;
    04     public static int ENGINEER = 0;
    05     public static int SALEMAN = 1;
    06     public static int MANAGER = 2;
    07  
    08     public Employee(int type)
    09     {
    10         _type = type;
    11     }
    12  
    13     public int Type
    14     {
    15         get { return _type; }
    16         set { _type = value; }
    17     }
    18  
    19  
    20 }
    21  
    22 public class ENGINEER : Employee
    23 {
    24     public int GetType()
    25     {
    26         return Employee.ENGINEER;
    27     }
    28 }
    29  
    30 public class SALEMAN : Employee
    31 {
    32     public int GetType()
    33     {
    34         return Employee.SALEMAN;
    35     }
    36 }
    37  
    38 public class MANAGER : Employee
    39 {
    40     public int GetType()
    41     {
    42         return Employee.MANAGER;
    43     }
    44 }
    45  
    46 public class Factory:Employee
    47 {
    48     public Employee Create(int type)
    49     {
    50         switch (type)
    51         {
    52             case ENGINEER:
    53                 return new ENGINEER();
    54             case SALEMAN:
    55                 return new SALEMAN();
    56             case MANAGER:
    57                 return new MANAGER();
    58             default:
    59                 throw new ExecutionEngineException("Incorrect type code value");
    60         }
    61     }
    62 }

    二、Replace Type Code with State/Strategy（以State/Strategy取代型别码）

    动机（Motivation）

    以State object（专门用来描述状态的对象）取代type code。

    示例

    view sourceprint?
    01 public class Employee
    02 {
    03     private int _type;
    04     public static int ENGINEER = 0;
    05     public static int SALEMAN = 1;
    06     public static int MANAGER = 2;
    07  
    08     public Employee(int type)
    09     {
    10         _type = type;
    11     }
    12  
    13     public int Type
    14     {
    15         get { return _type; }
    16         set { _type = value; }
    17     }
    18  
    19     public int PayAmount()
    20     {
    21         switch (_type)
    22         {
    23             case ENGINEER:
    24                 return 100;
    25             case SALEMAN:
    26                 return 1000;
    27             case MANAGER:
    28                 return 10000;
    29             default:
    30                 throw new ExecutionEngineException("Incorrect type code value");
    31         }
    32     }
    33  
    34 }

    改为

    view sourceprint?
    01 public class Employee
    02 {
    03     private int _type;
    04     public static int ENGINEER = 0;
    05     public static int SALEMAN = 1;
    06     public static int MANAGER = 2;
    07  
    08     public Employee(int type)
    09     {
    10         _type = type;
    11     }
    12  
    13     public int Type
    14     {
    15         get { return _type; }
    16         set { _type = value; }
    17     }
    18  
    19     public int PayAmount()
    20     {
    21         EmployeeType employeeType;
    22         switch (_type)
    23         {
    24             case ENGINEER:
    25                 employeeType= new ENGINEER();
    26                 break;
    27             case SALEMAN:
    28                 employeeType=new SALEMAN();
    29                 break;
    30             case MANAGER:
    31                 employeeType = new MANAGER();
    32                 break;
    33             default:
    34                 throw new ExecutionEngineException("Incorrect type code value");
    35         }
    36         return employeeType.GetType();
    37     }
    38  
    39 }
    40  
    41 public class ENGINEER : EmployeeType
    42 {
    43     public override  int GetType()
    44     {
    45         return 100;
    46     }
    47 }
    48  
    49 public class SALEMAN : EmployeeType
    50 {
    51     public override int GetType()
    52     {
    53         return 1000;
    54     }
    55 }
    56  
    57 public class MANAGER : EmployeeType
    58 {
    59     public override int GetType()
    60     {
    61         return 10000;
    62     }
    63 }
    64  
    65 public abstract class EmployeeType
    66 {
    67     public abstract int GetType();
    68  
    69 }

    三、Replace Subclass with Fields（以值域取代子类）

    动机（Motivation）

    修改这些函数，使它们返回superclass中的某个（新增值域，然后销毁subclasses）

    示例

    view sourceprint?
    01 public abstract class Person
    02 {
    03    public  abstract bool IsMale();
    04    public  abstract string GetCode();
    05  
    06    public Person CreateMale()
    07    {
    08        return new  Male();
    09    }
    10  
    11    public Person CreateFemale()
    12    {
    13        return new Female();
    14    }
    15 }
    16  
    17 public class Male : Person
    18 {
    19  
    20     public override bool IsMale()
    21     {
    22         return true;
    23     }
    24  
    25     public override string GetCode()
    26     {
    27         return "M";
    28     }
    29 }
    30  
    31 public class Female : Person
    32 {
    33  
    34     public override bool IsMale()
    35     {
    36         return false;
    37     }
    38  
    39     public override string GetCode()
    40     {
    41         return "F";
    42     }
    43 }

    改为

    view sourceprint?
    01 public class Person
    02 {
    03     private bool _IsMale;
    04     private string _Code;
    05  
    06     public bool IsMale
    07     {
    08         get { return _IsMale; }
    09         set { _IsMale = value; }
    10     }
    11  
    12     public string Code
    13     {
    14         get { return _Code; }
    15         set { _Code = value; }
    16     }
    17     public Person(bool isMale, string code)
    18     {
    19         this._IsMale = isMale;
    20         this._Code = code;
    21     }
    22 }
    23  
    24 public class Male : Person
    25 {
    26  
    27     public Male()
    28         : base(true, "M")
    29     { }
    30 }
    31  
    32 public class Female : Person
    33 {
    34     public Female()
    35         : base(false, "F")
    36     { }
    37 }

    四、Decompose Conditional（分解条件式）

    动机（Motivation）

    从if、then、else三个段落中分别提炼出独立函数。

    示例

    view sourceprint?
    1 if(date<SUMMER_START||date>SUMMER_BND)
    2    charge=quantity*_winterRate+_winterServiceCharge;
    3 else
    4     charge=quantity*_summerRate;

    改为

    view sourceprint?
    1 if(notSummer(date))
    2    charge=winterCharge(quantity);
    3 else
    4     charge=summerCharge(quantity);

    五、Consolidate Conditional Expression（合并条件式）

    动机（Motivation）

    将很多条件合并成一个条件式，并将这个条件式提炼成为一个独立函数。

    示例

    view sourceprint?
    1 public double DisabilityAmount()
    2 {
    3     if (_seniority < 2) return 0;
    4     if (_monthsDisabled > 12) return 0;
    5     if (_isPartTime) return 0;
    6     return 1;
    7 }

    改为

    view sourceprint?
    1 public double DisabilityAmount()
    2 {
    3     if (IsNotBligableForDisability()) return 0;
    4     return 1;
    5 }

    六、Consolidate Duplicate Conditional Fragments（合并重复的条件片段）

    动机（Motivation）

    将重复代码搬移到条件式之外。

    示例

    view sourceprint?
    01 if (isSpecialDeal())
    02 {
    03     total = price * 0.95;
    04     sendMail();
    05 }
    06 else
    07 {
    08     total = price * 0.98;
    09     sendMail();
    10 }

    改为

    view sourceprint?
    1 if (isSpecialDeal())
    2     total = price * 0.95;
    3 else
    4     total = price * 0.98;
    5  
    6 sendMail();
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  • 原文地址：https://www.cnblogs.com/zpq521/p/2067572.html
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