Инициализация исключительной ситуации

Автор: Xavier Pacheco

{
Copyright © 1999 by Delphi 5 Developer's Guide - Xavier Pacheco and Steve Teixeira
}

unit MainFrm;

interface

uses
  SysUtils, Windows, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls, AppEvnts, Buttons;

type

  ENotSoBadError = class(Exception);
  EBadError = class(Exception);
  ERealBadError = class(Exception);

  TMainForm = class(TForm)
    btnNotSoBad: TButton;
    btnBad: TButton;
    btnRealBad: TButton;
    appevnMain: TApplicationEvents;
    procedure btnNotSoBadClick(Sender: TObject);
    procedure btnBadClick(Sender: TObject);
    procedure btnRealBadClick(Sender: TObject);
    procedure appevnMainException(Sender: TObject; E: Exception);
  public
  end;

var
  MainForm: TMainForm;

implementation

{$R *.DFM}

procedure TMainForm.btnNotSoBadClick(Sender: TObject);
begin
  raise ENotSoBadError.Create('This isn''t so bad!');
end;

procedure TMainForm.btnBadClick(Sender: TObject);
begin
  raise EBadError.Create('This is bad!');
end;

procedure TMainForm.btnRealBadClick(Sender: TObject);
begin
  raise ERealBadError.Create('This is real bad!');
end;

procedure TMainForm.appevnMainException(Sender: TObject; E: Exception);
var
  rslt: Boolean;
begin
  if E is EBadError then
  begin
    { Show a custom message box and prompt for application termination. }
    rslt := MessageDlg(Format('%s %s %s %s %s', ['An', E.ClassName,
      'exception has occurred.', E.Message, 'Quit App?']),
        mtError, [mbYes, mbNo], 0) = mrYes;
    if rslt then
      Application.Terminate;
  end
  else if E is ERealBadError then
  begin // Show a custom message
    // and terminate the application.
    MessageDlg(Format('%s %s %s %s %s', ['An', E.ClassName,
      'exception has occured.', E.Message, 'Quitting Application']),
        mtError, [mbOK], 0);
    Application.Terminate;
  end
  else // Perform default exception handling
    Application.ShowException(E);
end;

end.