我有個TForm,佢有個Tedit叫做username,另外我有個function叫checkvalid,個checkvalid係private function,但為什麼checkvalid係做唔到username.text呢?但係係其它form到就可以username.text?點解,唔係同一張form的就可以嗎?

迷語< >< > Better post some of your code.. Or something like:

TForm1 = class (TForm)
    username: TEdit;
private
    function checkvalid: boolean;
end;

Or, is checkvalid a ordinal function not object method?

unit Login; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, Buttons; type TLoginForm = class(TForm) LoginNameLabel: TLabel; LoginNameEdit: TEdit; PasswordLabel: TLabel; PasswordEdit: TEdit; ConfirmButton: TBitBtn; CancelButton: TBitBtn; procedure ConfirmButtonClick(Sender: TObject); private { Private declarations } function DoLogin: Boolean; public { Public declarations } end; var LoginForm: TLoginForm; implementation {$R *.dfm} procedure TLoginForm.ConfirmButtonClick(Sender: TObject); begin if DoLogin = true then begin ModalResult := mrOk; end else begin ModalResult := mrNone; end; end; function TLoginForm.DoLogin() : Boolean; begin if StrLen(LoginNameEdit.text) = 0 then begin LoginNameEdit.SetFocus; Result := False; Exit; end; if StrLen(PasswordEdit.Text) = 0 then begin PasswordEdit.SetFocus; Result := False; Exit; end; end; end. ** 係dologin個到係call唔到LoginNameEdit.text Why?

Your problem is StrLen... function StrLen(const Str: PChar): Cardinal; TEdit.Text is a string. Change StrLen to length.

PChar?? Point of Char 同string有咩分別?係咪無'\n'分別?

Application.MessageBox('abc' IntToStr(m_MaxLoginTimes) 'def', MB_OK); 不是pchar,那怎麼轉換?

PChar is a pointer to a character (usually an array of characters) and often used as null terminated string. string default to huge (ansi) string, it is a dynamic string and there is no need for the null. Application.MessageBox(PChar('abc' IntToStr(m_MaxLoginTimes) 'def'), MB_OK);

係c 個度,string係有'\n',咁即係有點唔同啦... 同麻想問多少少野,係咪所有class,如TForm, TButton or PChar()等等...佢括號裏的野pass左之後,return 都係個個相對class,如TForm, TButton or PChar...

'\n' is linefeed in C , not necessary included in a string. C/C strings are null terminated while Delphi strings are not. TForm(xxx), PChar(xxx) are typecasting in Delphi.

sorry,我打錯了,應該是'\n'-->'\0' ~"~;; 另外,c 好似都有個叫cstring/string的data type,那它也是有'\0'嗎? 謝謝你的解答,原來delphi有typecasting(同c 一樣),如TForm和TFormclass等等...

cstring and string are classes in C .

原來如此,是我弄錯了,謝謝你的指教 ^_^