How to delete a specific line from a text file in Delphi

Question

I have a text file with user information stored in it line by line. Each line is in the format: UserID#UserEmail#UserPassword with '#' being the delimiter.

I have tried to use this coding to perform the task:

var sl:TStringList;
begin
  sl:=TStringList.Create;
  sl.LoadFromFile('filename');
  sl.Delete(Index);
  sl.SaveToFile('filename');
  sl.free;
end;

But I'm not sure what to put in the "index" space.

Is there any way I can receive the User ID as input and then delete the line of text from the text file that has this user ID in? Any help would be appreciated.

Answer 1

You can set the NameValueSeparator to # then use IndexOfName to find the user, as long as the username is the first value in the file.

sl.NameValueSeparator := '#';
Index := sl.IndexOfName('455115')

So in your example, like so

var sl:TStringList;
begin
  sl:=TStringList.Create;
  sl.LoadFromFile('filename');
  sl.NameValueSeparator := '#';
  Index := sl.IndexOfName('455115')
  if (Index  <> -1) then
  begin
      sl.Delete(Index);
      sl.SaveToFile('filename');
  end;
  sl.free;
end;

This may be slow on large files as IndexOfName loops though each line in the TStringList and checks each string in turn until it finds a match.

Disclaimer: Tested/ works with Delphi 2007, Delphi 7 may be diffrent.