Delphi StringBuilder

Question

Exists in Delphi something like the Java or C# StringBuilder? Or Delphi does not need StringBuilder and s := s + 'some string'; is good expression (mainly in for, while loops).

Answer 1

Yes, Delphi offers TStringBuilder (since version 2009):

procedure TestStringBuilder;
var
  I: Integer;
  StringBuilder: TStringBuilder;
begin
  StringBuilder := TStringBuilder.Create;
  try
    for I := 1 to 10 do
    begin
      StringBuilder.Append('a string ');
      StringBuilder.Append(66); //add an integer
      StringBuilder.Append(sLineBreak); //add new line
    end;

    OutputWriteLine('Final string builder length: ' +
                    IntToStr(StringBuilder.Length));
  finally
    StringBuilder.Free;
  end;
end;

And yes, you are right. s := s + 'text'; isn't really slower than using TStringBuilder.

Answer 2

In older Delphis, you can use Hallvard Vassbotn's HVStringBuilder. I failed to find the sources on his blog, but you can fetch them in the OmniThreadLibrary source tree, for example (you'll need files HVStringBuilder.pas and HVStringData.pas).

Answer 3

The TStringBuilder mentioned is the way to go. In your specific case concatenation may be fine, but I'd always try the alternative anyway.

I am creating an EPUB body content xhtml file in memory (Delphi XE) and it was taking so long to produce it that I never once let it finish (about 5 minutes plus before abandoning). This is a real life example combining around 800,000 characters of text. Taking the EXACT same code and directly replacing the s:=s+'' style statements with TStringBuilder.Append statements reduced it to around 3 seconds. To reiterate, there were no logic changes beyond a switch away from concatenation.

Answer 4

Delphi does not "REQUIRE" a string builder class, but one is provided for Delphi 2009 if you so desire to use it. Your example of s := s + 'some string'; is a typical method of concatinating strings and has been used in Pascal/Delphi for the past few decades without any significant problems.