Delphi validate two decimal places 0.005 equals 0

Question

I have a textedit component and a button component. The button component will add the textedit component text value to a list if that value is greater than 0. On the textedit component I can as many decimal places as I want, but I'd like to validate two decimal places. Like If I put 00.0032 in the textedit component the validation will take that as 0. Is there a function that will allow me to do this or do I have to do this by my own code.

This is my code

if (Trim(textEdit.Text) <> '') and (StrToCurr(Trim(textEdit.Text)) <> 0) then
begin      
  code to add the value 
end;

if tryStrToFloat(Edit1.text, value) and (value>0.005) then {some code to add value to list}. Also checks that value is number. — Yuriy Afanasenkov, Jul 18 '16 at 19:39
Don't use StrToFloat is your data is decimal. That produces binary floating point. — David Heffernan, Jul 18 '16 at 19:47
Oh, I saw "currency" tag on your question. Then you probably need var value:currency; begin if tryStrToCurr(Edit1.text, value) and (value>0.005) then ... — Yuriy Afanasenkov, Jul 18 '16 at 19:49
A terrible plug, I know, but just use my [BigDecimal](http://rvelthuis.de/programs/bigdecimals.html) type, or my [Decimal](http://rvelthuis.de/programs/decimals.html) type for such problems. Decimal allows a precision of up to 28 digits, BigDecimal an almost unlimited number of digits. The latter is very good at rounding to any number of decimal digits as well. — Rudy Velthuis, Jul 18 '16 at 21:45
I tried `if TryStrToCurr(textEdit.text, value) and (value> 0.005) then` and it worked. Thanks — Juan Felipe Gomez, Jul 19 '16 at 12:02

score 1 · Accepted Answer · answered Jul 20 '16 at 08:25

Reading your question two possible solutions come to my mind:

You could convert to float multiply by 100 (to shift by two decimals) and round using floor:

(Floor(StrToFloat(Trim(textEdit.Text)) * 100) <> 0)

This performs a conversion to floating point which might be slow.
An other solution could be to use string functions:

(StrToCurr(Copy(textEdit.Text, 1, Pos('.', textEdit.Text) + 2)) <> 0)

This copies the input string from beginning to two digits after the decimal separator '.'. Don't worry if your string is shorter (for example '0.1') you won't get an error.

Which solution is ultimately fast would have to be benchmarked.

Also have in mind, that not in every region a '.' is the decimal separator. In most of Europe for example decimal separator is ',' and thousands separator is '.'. Find out about TFormatSettings.

PS: You don't need to Trim before using StrToCurr because it does a trim internally.

Delphi validate two decimal places 0.005 equals 0

1 Answers1