Handbook之008：按值传递 与 按址传递

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

var
  Form1: TForm1;

implementation

{$R *.dfm}

function DubleValue(var AValue: Integer): Integer;
begin
  AValue := AValue * 2;
end;

function VarDubleValue(AValue: Integer): Integer;
begin
  AValue := AValue * 2;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  X: Integer;
  Y: Integer;
begin
  X := 10;
  DubleValue(X);
  Memo1.Lines.Add(‘按址传递‘ + X.ToString);

  Y := 10;
  VarDubleValue(Y);
  Memo1.Lines.Add(‘按值传递‘ + Y.ToString);
end;

end.