Handbook之004：编译器条件编译

关键代码如下：

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Memo1: TMemo;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
{$DEFINE TEST}

procedure TForm1.Button1Click(Sender: TObject);
begin
{$IFDEF TEST}
  Memo1.Lines.Add('曾经沧海难为水');
{$ENDIF}
{$IFNDEF TEST}
  Memo1.Lines.Add('曾经沧海难为水');
{$ENDIF}
end;

end.