Handling of numerical data entry 1

[pmravdin]

I want to have the user enter into 2 data entry fields numbers (integer or decimal). I would use SpinEdit but of course that will not handle decimals.
I am a little surprised that the Properties would make this trivial. Specifying a number with limits max min limits and an error message or non entry of information for NAN. Still I am learning a little Delphi and I am probably overlooking the obvious. Still looking at the books and help files has not made it obvious.
Could you help me gain a little insite into this?

 

[footpad]

pmravdin,

I'm sorry. I'm having trouble following the problem. Are you getting an error message? If so, what is it? Does this error appear consistently or only when certain values are provided? What are those values?

Thanks in advance....

-- Lance

 

[pmravdin]

Basically I want to let the user enter 2 decimal numbers and the program to multiply them.
2.1 * 4.3
I want to have error states if someone enters not a number. I realize that this is trivial, but I am a little surprised that that there is a component that makes specifies that it be a real number. Or something in ActiveX to do this.
I don't want to reinvent the wheel. Is there something trivial that will do this??

 

[bbegley]

You can do the string to float conversion inside a try except block

function IsNumeric(AString:string):double;
begin
try
result := StrToFloat(AString);
except
showmessage('Number required');
end;

If you want to clear the field if the value is not valid, you can pass in the component like this

function IsNumeric(AEdit:TCustomEdit):boolean;
begin
try
result := false;
StrToFloat(AEdit.Text);
result := true;
except
begin
ShowMessage('This field requires a numeric value.');
AEdit.Clear;
AEdit.SetFocus;
end;
end;

 

[bbegley]

Call the above function on Exit event.

 

[LucieLastic]

You could check the keys entered in the onKeyPress event, if the result isn't valid, ignore the key pressed.

procedure TForm1.edit1KeyPress(Sender: TObject; var Key: Char);
begin
if edit1.Text = '' then exit;
if not (key in [#13,'0'..'9','.',',', #8,'-']) then
key := #0;
if key in ['0'..'9','.',',','-'] then
Try
StrToFloat(edit1.Text+key);
except
key := #0;
end;
end;

lou

 

[Robertio]

Alternatively, you could just use the TMaskEdit component and set the editmask. Robertio
Alias: Robbie Calder
Software Developer
urc@walkermartyn.co.uk