无论实际值如何，条件始终评估为真

Question

我创建了一个 if 语句，当输入的代码与生成的代码匹配时，我想使用 `ShowMessage() 函数输出一条消息。但是，它仍然输出“干得好！”即使是明显错误的消息。

按钮代码：

procedure TfrmCAPTCHA.btnCheckClick(Sender: TObject);
var
  sCode, sAnswer : string;
  bRightAnswer, bWrongAnswer : boolean;
begin

  {button to verify input}

  sANswer := Trim(edtAnswer.Text);
  sCode := edtCaptchaCode.Text;

  bRightAnswer := (sAnswer = sCode);
  bRightAnswer := True;

  bWrongAnswer := (sAnswer <> sCode);
  bWrongAnswer := False;

  if bRightAnswer then  
  begin
    btnCAPTCHAContinue.Show;
    Showmessage('Nicely Done, seems you''''re all set to go!' + #13 +
                'Press the continue button to collect your codes young wizzling');
  end
  else begin
    edtCAPTCHACode.clear;
    edtAnswer.clear;
    btnCAPTCHAContinue.Hide;
    Showmessage( 'That seems to be the wrong answer, please try again');
  end;
end;

Answer 1

那是因为你先把bRightAnswer设置成true/false看是否正确，然后你马上又用固定的true覆盖了一遍不管条件。同样的事情在下一个块设置 bWrongAnswer 到 false:

  bRightAnswer := (sAnswer = sCode); 
  bRightAnswer := True;     {regardless of what it was before, it's always true now}

  bWrongAnswer := (sAnswer <> sCode);
  bWrongAnswer := False;    {regardless of what it was before, it's always false now}

删除这两行。

您可以通过将 bWrongAnswer := (sAnswer <> sCode); 替换为 bWrongAnswer := not bRightAnswer; 来进一步简化代码，或者更进一步并完全删除 bWrongAnswer 变量并仅在所有位置使用 not bRightAnswer你的代码。

其实现在看来，反正你连bWrongAnswer都用不着，直接去掉应该没什么坏处。

如果您愿意，也可以删除 bRightAnswer 并将 if bRightAnswer then 直接替换为 if sAnswer = sCode then。

无论实际值如何，条件始终评估为真

Condition always evaluates to true regardless of actual values

delphi

if-statement

boolean