Record Helpers for Intrinsic Types, Part 2 – Update

This week I used some record helpers for intrinsic types and I think that they are a wonderful feature. This means that you should update at least to XE3 to use this great feature.

But as always there are some issues: I had an resourcestring and wanted to access to the length.

program TestHelper;

{$APPTYPE CONSOLE}

uses
  System.SysUtils;

resourcestring
  SAnswer = '42';

begin
  Writeln('The length of ' + SAnswer + ' is:');
  Writeln(SAnswer.Length);
  Readln;
end.

I tried to compile this code and it doesn’t! The compiler doesn’t know the method length although in System.SysUtils there is the TStringHelper with this method! I had been very surprised but then I thought that a resourcestring is not a string but only assignable to a string, something like a type string.

With XE4 this code does compile which is the expected behavior! Many thanks for this fix.

I talked about this issue to a friend (Many thanks to him!) and he told me that I should try a record helper for a WideString.

program TestHelper;

{$APPTYPE CONSOLE}

uses
  System.SysUtils;

resourcestring
  SAnswer = '42';

type
  TWideStringHelper = record helper for WideString
  public
    function Length: Integer; inline;
  end;

{ TWideStringHelper }

function TWideStringHelper.Length: Integer;
begin
  Result := System.Length(Self);
end;

begin
  Writeln('The length of ' + SAnswer + ' is:');
  Writeln(SAnswer.Length);
  Readln;
end.

And this code does compile! This means that a resourcestring is a WideString. Again, I’m surprised. But run this small project. It shows that the length of ’42’ is 1. This is a bug!!! My friend told me that a there is already the Quality Central item 112844 for this bug. This means that you shouldn’t use a record helper for resourcestrings in XE3. I hope that this bug will be fixed in XE4, so stay tuned….

Again, under XE4 the resourcestring works like a string. This means that a TWideStringHelper doesn’t work, instead the TStringHelper does. And the length is the correct value. So many thanks for this fix. This is a very good reason to move to XE4.