重构 -- 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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

public abstract class Person {    public  abstract bool IsMale();    public  abstract string GetCode();      public Person CreateMale()    {        return new  Male();    }      public Person CreateFemale()    {        return new Female();    } }   public class Male : Person {       public override bool IsMale()     {         return true;     }       public override string GetCode()     {         return "M";     } }   public class Female : Person {       public override bool IsMale()     {         return false;     }       public override string GetCode()     {         return "F";     } }

 

改为

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

public class Person {     private bool _IsMale;     private string _Code;       public bool IsMale     {         get { return _IsMale; }         set { _IsMale = value; }     }       public string Code     {         get { return _Code; }         set { _Code = value; }     }     public Person(bool isMale, string code)     {         this._IsMale = isMale;         this._Code = code;     } }   public class Male : Person {       public Male()         : base(true, "M")     { } }   public class Female : Person {     public Female()         : base(false, "F")     { } }