1 之前我们可以定义方法类型, 然后通过方法类型的变量来使用方法, 譬如:
  2 --------------------------------------------------------------------------------
  3  
  4 unit Unit1;
  5 
  6 interface
  7 
  8 uses
  9   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 10   Dialogs;
 11 
 12 type
 13   TForm1 = class(TForm)
 14     procedure FormCreate(Sender: TObject);
 15   end;
 16 
 17 var
 18   Form1: TForm1;
 19 
 20 implementation
 21 
 22 {$R *.dfm}
 23 
 24 Type
 25   TFun = function(const num: Integer): Integer; {先定义一个方法类型}
 26 
 27   function MySqr(const num: Integer): Integer;  {再创建一个吻合上面类型的一个方法}
 28   begin
 29     Result := num * num;
 30   end;
 31 
 32 {测试}
 33 procedure TForm1.FormCreate(Sender: TObject);
 34 var
 35   fun: TFun;  {方法变量}
 36   n: Integer;
 37 begin
 38   fun := MySqr;             {给变量赋值为相同格式的方法}
 39   n := fun(9);              {现在这个方法变量可以使用了}
 40   ShowMessage(IntToStr(n)); {81}
 41 end;
 42 
 43 end.
 44 ----------------------------之所以这样做, 是因为有时需要把 "方法" 当作参数, 譬如:
 45 --------------------------------------------------------------------------------
 46  
 47 unit Unit1;
 48 
 49 interface
 50 
 51 uses
 52   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 53   Dialogs;
 54 
 55 type
 56   TForm1 = class(TForm)
 57     procedure FormCreate(Sender: TObject);
 58   end;
 59 
 60 var
 61   Form1: TForm1;
 62 
 63 implementation
 64 
 65 {$R *.dfm}
 66 
 67 Type
 68   TFun = function(const num: Integer): Integer; {先定义一个方法类型}
 69 
 70   function MySqr(const num: Integer): Integer;  {再创建一个吻合上面类型的一个方法}
 71   begin
 72     Result := num * num;
 73   end;
 74 
 75   {把方法当作参数的方法}
 76   procedure MyProc(var x: Integer; fun: TFun);
 77   begin
 78     x := fun(x);
 79   end;
 80 
 81 {测试}
 82 procedure TForm1.FormCreate(Sender: TObject);
 83 var
 84   n: Integer;
 85 begin
 86   n := 9;
 87   MyProc(n, MySqr);
 88   ShowMessage(IntToStr(n)); {81}
 89 end;
 90 
 91 end.
 92 -------------现在 Delphi 2009 可以使用匿名方法了(使用 reference 定义方法类型, 然后在代码中随用随写方法), 譬如:
 93 --------------------------------------------------------------------------------
 94  
 95 unit Unit1;
 96 
 97 interface
 98 
 99 uses
100   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
101   Dialogs;
102 
103 type
104   TForm1 = class(TForm)
105     procedure FormCreate(Sender: TObject);
106   end;
107 
108 var
109   Form1: TForm1;
110 
111 implementation
112 
113 {$R *.dfm}
114 
115 Type
116   TFun = reference to function(const num: Integer): Integer; {用 reference 定义匿名方法类型}
117 
118 procedure TForm1.FormCreate(Sender: TObject);
119 var
120   fun: TFun;
121   n: Integer;
122 begin
123   {求平方}
124   fun := function(const a: Integer): Integer {注意本行最后不能有 ; 号}
125   begin
126     Result := a * a;
127   end;
128 
129   n := fun(9);
130   ShowMessage(IntToStr(n)); {81}
131 
132   {求倍数}
133   fun := function(const a: Integer): Integer
134   begin
135     Result := a + a;
136   end;
137 
138   n := fun(9);
139   ShowMessage(IntToStr(n)); {18}
140 end;
141 
142 end.
143 --------------------------------------------------------------------------------把匿名方法当作其他方法的参数:
144 --------------------------------------------------------------------------------
145  
146 unit Unit1;
147 
148 interface
149 
150 uses
151   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
152   Dialogs;
153 
154 type
155   TForm1 = class(TForm)
156     procedure FormCreate(Sender: TObject);
157   end;
158 
159 var
160   Form1: TForm1;
161 
162 implementation
163 
164 {$R *.dfm}
165 
166 Type
167   TFun = reference to function(const num: Integer): Integer;
168 
169   function FunTest(const n: Integer; fun: TFun): string;
170   begin
171     Result := Format('%d, %d', [n, fun(n)]);
172   end;
173 
174 procedure TForm1.FormCreate(Sender: TObject);
175 var
176   f: TFun;
177   s: string;
178 begin
179   f := function(const a: Integer): Integer {注意本行最后不能有 ; 号}
180   begin
181     Result := a * a;
182   end;
183 
184   s := FunTest(9, f);
185 
186   ShowMessage(s); {9, 81}
187 end;
188 
189 end.

1 procedure MySelf(Const Value:Integer);
2 begin
3      Case  Value of
4        0:  MyProc(n, MySqr);
5        1:  MyProc(M, NewSqr);
6        3: ...........
7      end;
8 end;