delphi中 注意一点，record 类型 参数默认是 值拷贝，class 参数 默认是传地址；值传递，指针传递、引用传递

作为函数的入参，若是record类型，默认是值拷贝，效率低，若要传指针，需要加 var ;

作为函数的入参，若是 class类型，默认是传地址，不需要加var

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

  TDataWarp = class
    a: Integer;
    b: Integer;
  end;

  TForm1 = class(TForm)
    Button1: TButton;
    mmo1: TMemo;
    procedure swap2(Sender: TObject;  dw: TDataWarp);
    procedure Button1Click(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);

  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  ReportMemoryLeaksOnShutdown := True;
end;

procedure TForm1.swap2(Sender: TObject; dw: TDataWarp);
var
  tmp: Integer;
begin
  tmp := dw.a;
  dw.a := dw.b;
  dw.b := tmp;

  mmo1.Lines.Add(dw.a.ToString);

  dw := nil;
  dw.Free;

end;

procedure TForm1.Button1Click(Sender: TObject);
var
  dw: TDataWarp;
begin
  dw := TDataWarp.Create;
  dw.a := 6;
  dw.b := 9;
  swap2(Sender, dw);
  mmo1.Lines.Add(dw.a.ToString);
  dw.Free;

end;

end.