1
2 //Pass a component as TComponent generically,
3 //and change a property value
4 //- only if the component publishes that property -
5 //without typecasting.
6
7 unit Unit1;
8
9 interface
10
11 uses
12 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
13 Dialogs,TypInfo, StdCtrls, ExtCtrls;
14
15 type
16 TForm1 = class(TForm)
17 Edit1: TEdit;
18 Memo1: TMemo;
19 CheckBox1: TCheckBox;
20 RadioGroup1: TRadioGroup;
21 procedure FormCreate(Sender: TObject);
22 private
23 { Private declarations }
24 public
25 { Public declarations }
26 end;
27
28 var
29 Form1: TForm1;
30
31 implementation
32
33 {$R *.dfm}
34
35 uses
36 TypInfo;
37
38 procedure ChangeProperty(C: TComponent; const Name: string; Val: string);
39 var
40 PropInfo: TypInfo.PPropInfo;
41 begin
42 PropInfo:= GetPropInfo(C.ClassInfo, Name);
43 if PropInfo <> nil then TypInfo.SetPropValue(C, Name, Val);
44 end;
45
46 //This example will change the Text property
47 //of every component on the form
48 //if the component owns a PUBLISHED Text property;
49 //otherwise it will skip the component.
50
51 procedure TForm1.FormCreate(Sender: TObject);
52 var
53 i: Integer;
54 begin
55 for i:= 0 to Pred(ComponentCount) do
56 ChangeProperty(Components[i], 'Text', 'Changed');
57 end;
58 //Check out TypInfo, it has many useful properties!
59
60 end.
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