Delphi - How can I extract the digits from a character string?

Question

I was developing a program that validate a CPF, a type of document of my country. I already did all the math. But in the input Edit1, the user will insert like:

123.456.789-00

I have to get only the numbers, without the hyphen and the dots, to my calcs worth.

I'm newbie with Delphi, but I think that's simple. How can I do that? Thanks for all

Perhaps, TRegEx.Replace(s, '\D', '')? (\D is a non-digit, and \W is a non-word character, both should work). — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 6, 2015 at 21:23

Wiktor Stribiżew · Accepted Answer · 2015-11-06 21:27:35Z

4

You can use

text := '123.456.789-00'
text := TRegEx.Replace(text, '\D', '')

Here, \D matches any non-digit symbol that is replaced with an empty string.

Result is 12345678900 (see regex demo).

answered Nov 6, 2015 at 21:27

Wiktor Stribiżew

631k41 gold badges502 silver badges632 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

David Heffernan · Accepted Answer · 2015-11-07 22:18:40Z

2

Using David's suggestion, iterate your input string and remove characters that aren't numbers.

{$APPTYPE CONSOLE}

function GetNumbers(const Value: string): string;
var
  ch: char;
  Index, Count: integer;
begin
  SetLength(Result, Length(Value));
  Count := 0;      
  for Index := 1 to length(Value) do
  begin
    ch := Value[Index];
    if (ch >= '0') and (ch <='9') then
    begin
      inc(Count);
      Result[Count] := ch;
    end;
  end;
  SetLength(Result, Count);
end;

begin
  Writeln(GetNumbers('123.456.789-00'));
  Readln;
end.

edited Nov 7, 2015 at 22:18

David Heffernan

616k46 gold badges1.1k silver badges1.5k bronze badges

answered Nov 6, 2015 at 22:13

John Easley

1,5801 gold badge14 silver badges24 bronze badges

6 Comments

David Heffernan Over a year ago

Be nice to avoid as many of those heap allocations as you can.

MartynA Over a year ago

@DavidHeffernan: Not meaning to be obtuse, but I'm curious about what you have in mind regarding "Be nice ...". Do you meant counting the number of digit occurrences first, then allocating space for the Result based on that, or what?

David Heffernan Over a year ago

@Martyn That. Or allocate string of same length as result, populate, and size before exit. Two heap allocs.

David Heffernan Over a year ago

@John Also worth pointing out that in with Unicode text will lead to warnings. I'd use (ch >= '0') and (ch <= '9')

David Heffernan Over a year ago

Yes. I corrected the off by one error. I'd still reduce the heap allocs were it me, but perhaps I'm being picky.

|

Collectives™ on Stack Overflow

Delphi - How can I extract the digits from a character string?

2 Answers 2

Comments

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related