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redirecting exception to a log file

boardtc
boardtc asked
on
Medium Priority
179 Views
Last Modified: 2010-04-06
I have all my error messages set up as exceptions. How can i set it up so that any exceptions occuring are written to a log file as well as the screen. (D1).

Thanks.

Tom.
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Commented:
Here is a very simple example of an exception logger in D1:

unit Main;

interface

uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls, Buttons, ExtCtrls, Menus;

type
  TMainForm = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    procedure MyExceptionHandler(Sender: TObject; E: Exception);
  end;

var
  MainForm: TMainForm;

implementation

{$R *.DFM}

procedure TMainForm.MyExceptionHandler(Sender: TObject; E: Exception);
var
  LogFile: TextFile;
begin
  AssignFile(LogFile, 'log.txt');
  if not FileExists('log.txt')
  then ReWrite(LogFile)
  else Append(LogFile);
  Writeln(LogFile, DateTimeToStr(Now), ': ', E.Message);
  CloseFile(LogFile);
end;

procedure TMainForm.FormCreate(Sender: TObject);
begin
  Application.OnException := MyExceptionHandler;
end;

procedure TMainForm.Button1Click(Sender: TObject);
var
  x: Real;
begin
  try
    x := x/0;
  except
  end;
end;

end.

Hope this is what you need!

/// John

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Commented:
Hmm-hmmm!
I screwed up! To handle the exceptions this way you have
to re-raise the exception after "except":

  try
    x := x/0;
  except
    raise
  end;

Or simply exclude the try-blocks...!

Sorry!

/// John

Author

Commented:
John,

Thanks. Simply a matter of assigning a procedure to the Application.OnException and then you can do as you want.

Cheers.

Tom.
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