是否有良好的做法，如果在循环TStringList项时避免了越界索引错误? [英] Are there good practices if any avoiding out of bounds index error when looping TStringList items?

问题描述

:)

第一件事，我的代码

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;

• 当for i:=0 to plik.Count-2 do时，我可以删除任何元素，但不能删除 最后.
• 当for i:=0 to plik.Count-1 do时，我可以删除没有 但从头到尾.因为否则列表索引将超出范围.
• 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.

怎么回事?如何安全搜索并从TStringList中删除元素?

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

推荐答案

从列表中删除intem时，您想使用downto循环，即

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;

这可以确保，如果删除项目，则循环索引在从列表末尾向列表末尾移动时仍保持有效.

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.

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