Question

🙂

First thing, my code

procedure TForm1.Button3Click(Sender: TObject);
var tempId,i:integer;
begin
tempId:=strtoint(edit5.Text);
plik:=TStringList.Create;
plik.LoadFromFile('.\klienci\'+linia_klient[id+1]+'.txt');
if (plik.Count=1) then
  begin
  label6.Caption:='then';
    if (tempId=StrToInt(plik[0])) then
      begin
      Label6.Caption:='Zwrócono';
      plik.Delete(0);
    end
  end
else
for i:=0 to plik.Count-2 do
  begin
    if (tempId=StrToInt(plik[i])) then
    begin
      Label6.Caption:='Zwrócono';
      plik.Delete(i);
    end;
  end;
plik.SaveToFile('.\klienci\'+linia_klient[id+1]+'.txt');
plik.Free;
end;

• When for i:=0 to plik.Count-2 do I can delete any element but not
  last.
• When for i:=0 to plik.Count-1 do I can delete any element without
  but from end to start. Because otherwise List index out of bounds.

What’s going one? How can I safety search and remove elements from TStringList?

Answer 1

When deleting intems from list you want to use downto loop, ie

for i := plik.Count-1 downto 0 do
  begin
    if (tempId=StrToInt(plik[i])) then
    begin
      Label6.Caption:='Zwrócono';
      plik.Delete(i);
    end;
  end;

This ensures that if you delete item, the loop index stays valid as you move from the end of the list dowards beginning of the list.