Question

delphi7中使用pchar('1')报错

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, DB, DBTables, Grids, DBGrids, StdCtrls, ComCtrls;

type
TForm1 = class(TForm)
ComboBox2: TComboBox;
procedure FormActivate(Sender: TObject);
procedure ComboBox2Change(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormActivate(Sender: TObject);
begin
ComboBox2.Clear;
ComboBox2.AddItem('是',TObject(pchar('1')));
ComboBox2.AddItem('否',TObject(pchar('2')));
ComboBox2.ItemIndex := 1;
end;

procedure TForm1.ComboBox2Change(Sender: TObject);
var str : String;
begin
str := '1';
showmessage(pchar('1'));

end;

end.

在调用showmessage(pchar('1'));
时报错
改成showmessage(pchar('10'));就能正常编译并整形，高手告诉我是什么原因呀

Answer 1

你写了个常量 '1' , delphi 编译器默认为Char型, 而这种Char后面没有#0结束字符,
而'10'则不同了,编译器默认为string型, string有个特点以 #0为结束标志,恰好pchar类型也是这种情况, 你写个'1',编译器会继续往后找#0,这样就可能访问越界出错,你的就是这种情况,如果你非要Show，则要这要写
Showmessage(Pchar('1'#0));

Answer 2

你已定义了str := '1';
就使用showmessage(str);

showmessage的参数类型是string