Help with Regex Validation
lazarus / 62-General

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jorge_mosquera · 2024-02-13 15:04

Hello, please help. I need to implement data validation using Regex,
for example to ensure that only one of these options is entered:
a- Only numbers
b- Only letters without space
c- Only letters with space
d- Date in dd/mm/yyyy format

For example, I am using this code to validate only numbers, but it
returns true if I enter numbers, numbers plus letters, when what I
expect is that when entering a character other than numbers, it
returns an error

Procedure TForm1.Button1Click(Sender: TObject);
var
  Regex : TRegExpr;
  band : boolean;
Begin
  Regex := TRegExpr.Create;
  case RadioGroup1.ItemIndex of
   0 : Regex.Expression := '\d+';
  End;
  if Regex.Exec(LabeledEdit1.Text)  then
   showmessage('Yes')
  else
    showmessage('no');
end;

Regards

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Fibonacci · 2024-02-13 15:13

Expression is invalid. It finds any decimal inside String, you need to
make sure there is nothing else before and after "\d", you do this
using ^ and $.

^\d+$

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Martin_fr · 2024-02-13 15:47

There are sites like https://regex101.com/ that can help. You can test
your regex there, and you get an explanation of what it does.

Depending on what feature you need, they may not all be in the
TRegExpr that comes with current fpc. The upstream project is ahead
and offers more.
https://github.com/andgineer/TRegExpr
Doc:
https://github.com/andgineer/TRegExpr/blob/master/docs/tregexpr.rst