Radio Buttons cause a "STACK OVERFLOW"

[OC DelGuy]

Why is there a "STACK OVERFLOW" error here?
When I first click any of the RB's it works fine.  But if I click a different button, then I get the error.

Code: Pascal  [Select][+][-]

1. unit RadButts;
2. {$mode objfpc}{$H+}
3. interface
4.  
5. uses
6.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls;
7.  
8. type
9.   { TForm1 }
10.  
11.   TForm1 = class(TForm)
12.     Solve: TButton;
13.     Edit1: TEdit;
14.     Edit2: TEdit;
15.     Edit3: TEdit;
16.     Memo1: TMemo;
17.     RadioButton: TLabel;
18.     RadioButton1: TRadioButton;
19.     RadioButton2: TRadioButton;
20.     RadioButton3: TRadioButton;
21.     RadioButton4: TRadioButton;
22.     RadioButton5: TRadioButton;
23.     procedure RadioButton1Change(Sender: TObject);
24.     procedure RadioButton2Change(Sender: TObject);
25.     procedure RadioButton3Change(Sender: TObject);
26.     procedure RadioButton4Change(Sender: TObject);
27.     procedure RadioButton5Change(Sender: TObject);
28.   end;
29.  
30. var
31.   Form1: TForm1;
32.  
33. implementation
34. {$R *.lfm}
35. { TForm1 }
36.  
37.   procedure TForm1.RadioButton1Change(Sender: TObject);
38.     begin
39.       If RadioButton1.Checked=False then
40.         Begin
41.           RadioButton1.Checked:=True;
42.           RadioButton2.Checked:=False;
43.           RadioButton3.Checked:=False;
44.           RadioButton4.Checked:=False;
45.           RadioButton5.Checked:=False;
46.         End;  { RadioButton1.Checked=False }
47.     end;  {proc RadioButton1Change}
48.  
49.   procedure TForm1.RadioButton2Change(Sender: TObject);
50.     begin
51.       If RadioButton2.Checked=False then
52.         Begin
53.           RadioButton1.Checked:=False;
54.           RadioButton2.Checked:=True;
55.           RadioButton3.Checked:=False;
56.           RadioButton4.Checked:=False;
57.           RadioButton5.Checked:=False;
58.         End;  { RadioButton2.Checked=False }
59.     end;  {proc RadioButton2Change}
60.  
61.   procedure TForm1.RadioButton3Change(Sender: TObject);
62.     begin
63.       If RadioButton3.Checked=False then
64.         Begin
65.           RadioButton1.Checked:=False;
66.           RadioButton2.Checked:=False;
67.           RadioButton3.Checked:=True;
68.           RadioButton4.Checked:=False;
69.           RadioButton5.Checked:=False;
70.         End;  { RadioButton3.Checked=False }
71.     end;  {proc RadioButton3Change}
72.  
73.   procedure TForm1.RadioButton4Change(Sender: TObject);
74.     begin
75.       If RadioButton4.Checked=False then
76.         Begin
77.           RadioButton1.Checked:=False;
78.           RadioButton2.Checked:=False;
79.           RadioButton3.Checked:=False;
80.           RadioButton4.Checked:=True;
81.           RadioButton5.Checked:=False;
82.         End;  { RadioButton4.Checked=False }
83.     end;  {proc RadioButton4Change}
84.  
85.   procedure TForm1.RadioButton5Change(Sender: TObject);
86.     begin
87.       If RadioButton5.Checked=False then
88.         Begin
89.           RadioButton1.Checked:=False;
90.           RadioButton2.Checked:=False;
91.           RadioButton3.Checked:=False;
92.           RadioButton4.Checked:=False;
93.           RadioButton5.Checked:=True;
94.         End;  { RadioButton5.Checked=False }
95.     end;  {proc RadioButton5Change}
96.  
97. end.  {Implementation}
98.  

[Jorg3000]

Hi!
You create a recursion because you always create a new change in the change event (setting .Checked again).
This causes the change function to be called thousands of times until the stack overflows.

Do not make any changes to .Checked of the same control in a Change event.

[paweld]

The TradioButton component has it that changing one of them to selected automatically deselects the previously selected one - this applies to all RBs in the group (located on the same parent component).
Thus, all events in your code are unnecessary.

More info: https://wiki.lazarus.freepascal.org/TRadioButton

[cdbc]

Hi
As @paweld so correctly says it, thanks mate 
Meanwhile I made a small example for you, to look at and learn from...

eta: For others that can't bother to download, here's the pas-file:

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls, StdCtrls,
9.   ComCtrls;
10.  
11. type
12.  
13.   { TfrmMain }
14.   TfrmMain = class(TForm,IFPObserver)
15.     Panel1: TPanel;
16.     RadioButton1: TRadioButton;
17.     RadioButton2: TRadioButton;
18.     RadioButton3: TRadioButton;
19.     RadioButton4: TRadioButton;
20.     stbInfo: TStatusBar;
21.   private
22.     procedure FPOObservedChanged(ASender: TObject;
23.                                  Operation: TFPObservedOperation;
24.                                  {%H-}Data: Pointer);
25.     procedure HandleClick(aSender: TObject);
26.   public
27.     procedure AfterConstruction; override;
28.     procedure BeforeDestruction; override;
29.   end;
30.  
31. var
32.   frmMain: TfrmMain;
33.  
34. implementation
35.  
36. {$R *.lfm}
37.  
38. { TfrmMain }
39. procedure TfrmMain.FPOObservedChanged(ASender: TObject;
40.                                       Operation: TFPObservedOperation;
41.                                       Data: Pointer);
42. begin
43.   case Operation of
44.     ooChange: begin
45.                 if ASender is TComponent then
46.                   stbInfo.SimpleText:= TComponent(ASender).Name + ' is chosen :)';
47.               end;
48.   end;
49. end;
50.  
51. procedure TfrmMain.HandleClick(aSender: TObject);
52. begin
53.   (aSender as TRadioButton).FPONotifyObservers(aSender,ooChange,nil);
54. end;
55.  
56. procedure TfrmMain.AfterConstruction;
57. begin
58.   inherited AfterConstruction;
59.   RadioButton1.FPOAttachObserver(Self);
60.   RadioButton1.OnClick:= @HandleClick;
61.   RadioButton2.FPOAttachObserver(Self);  
62.   RadioButton2.OnClick:= @HandleClick;
63.   RadioButton3.FPOAttachObserver(Self);
64.   RadioButton3.OnClick:= @HandleClick;
65.   RadioButton4.FPOAttachObserver(Self);
66.   RadioButton4.OnClick:= @HandleClick;  
67.   RadioButton3.Checked:= true;
68. end;
69.  
70. procedure TfrmMain.BeforeDestruction;
71. begin /// important to remember detaching observers to avoid AVs
72.   RadioButton1.FPODetachObserver(Self);
73.   RadioButton2.FPODetachObserver(Self);
74.   RadioButton3.FPODetachObserver(Self);
75.   RadioButton4.FPODetachObserver(Self);
76.   inherited BeforeDestruction;
77. end;
78.  
79. end.
80.  
81.  

Regards Benny

[jamie]

maybe you can use this.

Code: Pascal  [Select][+][-]

1. procedure TForm1.RadioButton1Change(Sender: TObject);
2. begin
3.   With TRadioButton(Sender) do
4.    Begin
5.       If Tag = 0 Then Tag := 1 else Exit; //Busy state.
6.       // Do your code here.
7.      Tag := 0;
8.    end;
9. end;                                          
10.  

That will prevent a loop.
Jamie