Hi Tim,

I've been trying to work out how to validate the TEdit text property to make sure only integers are entered.  I found out something interesting (that works):

var
  UserAge: integer;

UserAge := StrToInt(edtAge.Text);
if IntToStr(UserAge) = 'NaN' then
begin
    // Not a valid number
end;

Does NaN stand for "Not a Number"?  Is this a bug or is this the correct way to check for numbers?

Steve

Steve


Does that work in Delphi as well? If so which version?

Normally I've used a try..except block to see if a number was a number. However, I'd generally use the OnKeyPress event to stop anything other than 0..9 being entered.

Roy Lambert

It is in Delphi too....

http://www.delphibasics.co.uk/RTL.asp?Name=NaN


Walter

Steve,

<< Does NaN stand for "Not a Number"?  Is this a bug or is this the correct
way to check for numbers? >>

This is one of those areas where native Delphi's OP and EWB's OP deviate.
If a string isn't a valid number, then you will not receive an exception,
rather the result will be NaN.  This also applies to floating-point numbers
(Double).

--
Tim Young
Elevate Software
www.elevatesoft.com

Walter


That's totally unrelated to Steve's post. It uses a specialised function (IsNaN) testing numbers. Steve has a StrToInt(string) = 'NaN' but AFAIK in Delphi (up to D2006) doesn't have an overridden version of StrToInt which would produce a string result.

Roy Lambert

Tim

>This is one of those areas where native Delphi's OP and EWB's OP deviate.
>If a string isn't a valid number, then you will not receive an exception,
>rather the result will be NaN. This also applies to floating-point numbers
>(Double).

That's what I wanted to know. Nice booby trap

Roy Lambert

Hi Tim,

<< This is one of those areas where native Delphi's OP and EWB's OP deviate.
If a string isn't a valid number, then you will not receive an exception,
rather the result will be NaN.  This also applies to floating-point numbers
(Double).  >>

Thanks, makes sense.  Yeah, I tried a try..except block first and found it didn't work.  Then I put a couple of ShowMessage's in to see what was coming back when I entered a non-number value.

Steve