unit1.pas

Delphi basic program. Basic programing guide for delphi language. Several samples are giving.

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
    PassWord: TEdit;
    InputEdit: TEdit;
    Label2: TLabel;
    Button1: TButton;
    Button2: TButton;
    procedure PassWordKeyPress(Sender: TObject; var Key: Char);
    procedure InputEditKeyPress(Sender: TObject; var Key: Char);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation
type
  EInValidation = class(Exception)
  public
  ErrorCode: Integer;
    constructor Create(Const Msg: String;ErrorNum: Integer);
  end;
  EInvalidPassWord = class(EInValidation)
  public
    constructor Create;
  end;
  EInvalidInput = class(EInValidation)
  public
    constructor Create(ErrorNum: Integer);
  end;


constructor EInValidation.Create(Const Msg: String; ErrorNum: Integer);
begin
  inherited Create(Msg);
  ErrorCode := ErrorNum;
end;

constructor EInValidPassWord.Create;
begin
  inherited Create('Invalid Password Entered',0);
end;

constructor EInValidInput.Create(ErrorNum: Integer);
var
  Msg: String;
begin
  case ErrorNum of
  1:
    Msg := 'Can not convert String to Number';
  2:
    Msg := 'Number is out of Range';
  else
    Msg := 'Input is Invalid';
  end;
  inherited Create(Msg,ErrorNum);
end;

{$R *.dfm}

procedure TForm1.PassWordKeyPress(Sender: TObject; var Key: Char);
const
  CurrentPassWord = 'Delphi';
begin
  if Key = #13 then
  begin
    try
      if PassWord.text <> CurrentPassWord then
        raise EInvalidPassWord.Create;
      Label2.Visible := True;
      InputEdit.Visible := True;
      InputEdit.SetFocus;
      PassWord.Visible := False;
      Label1.Visible := False;
    except
      on EInvalidPassWord do
      begin
        PassWord.text := '';
        raise;
      end;
    end;
    Key:=#0;
  end;
end;


procedure TForm1.InputEditKeyPress(Sender: TObject; var Key: Char);
var
  Res: Real;
  Code: Integer;
begin
  if Key = #13 then
begin
  try
    val(InputEdit.text,Res,Code);
    if Code <> 0 then
      raise EInValidInput.create(1);
    if (Res > 1) or (Res < 0) then
      raise EInValidInput.create(2);
      MessageDlg('Correct Input', mtInformation,[mbOk], 0);
      Key := #0;
      except
      on E:EInValidInput do
      begin
        InputEdit.text := '';
        MessageDlg(E.Message, mtWarning,[mbOk], 0);
      end;
    end;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
 Application.Terminate;
end;

end.