足让你打吃一惊：一小段奇异的代码

function TForm1.GetValue2(var s: string): Boolean;
begin
 Result := True;
 ShowMessage('af');//加上这行再试试，会发现没有执行
 s := 'World'; 
end;

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
        function GetTrue: Boolean;
    function GetValue1(var s: string): Variant;
    function GetValue2(var s: string): Boolean;

  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}



function TForm1.GetTrue: Boolean;
begin
  Result := True;
end;

function TForm1.GetValue1(var s: string): Variant;
begin
  s := 'World';
  Result := True;

end;

function TForm1.GetValue2(var s: string): Boolean;
begin
  Result := True;
  s := 'World';
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  s: string;
begin
  if GetTrue or GetValue1(s) then
    ShowMessage('Hello ' + s);
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  s: string;
begin
  if  GetValue2(s) or (GetTrue) then
    ShowMessage('Hello ' + s);
end;


end.