SetToString, StringToSet

The SetToString, StringToSet functions in TypInfo unit take PPropInfo as parameter which means you can only use them with set types for which RTTI (a published property) exists.

Here are my versions which take PTypeInfo instead so you can use them with set types in general, even without a published property declared for the type:

uses
  SysUtils, TypInfo;

function GetOrdValue(Info: PTypeInfo; const SetParam): Integer;
begin
  Result := 0;

  case GetTypeData(Info)^.OrdType of
    otSByte, otUByte:
      Result := Byte(SetParam);
    otSWord, otUWord:
      Result := Word(SetParam);
    otSLong, otULong:
      Result := Integer(SetParam);
  end;
end;

procedure SetOrdValue(Info: PTypeInfo; var SetParam; Value: Integer);
begin
  case GetTypeData(Info)^.OrdType of
    otSByte, otUByte:
      Byte(SetParam) := Value;
    otSWord, otUWord:
      Word(SetParam) := Value;
    otSLong, otULong:
      Integer(SetParam) := Value;
  end;
end;

function SetToString(Info: PTypeInfo; const SetParam; Brackets: Boolean): AnsiString;
var
  S: TIntegerSet;
  TypeInfo: PTypeInfo;
  I: Integer;
begin
  Result := '';

  Integer(S) := GetOrdValue(Info, SetParam);
  TypeInfo := GetTypeData(Info)^.CompType^;
  for I := 0 to SizeOf(Integer) * 8 - 1 do
    if I in S then
    begin
      if Result <> '' then
        Result := Result + ',';
      Result := Result + GetEnumName(TypeInfo, I);
    end;
  if Brackets then
    Result := '[' + Result + ']';
end;

procedure StringToSet(Info: PTypeInfo; var SetParam; const Value: AnsiString);
var
  P: PAnsiChar;
  EnumInfo: PTypeInfo;
  EnumName: AnsiString;
  EnumValue, SetValue: Longint;

  function NextWord(var P: PAnsiChar): AnsiString;
  var
    I: Integer;
  begin
    I := 0;
    // scan til whitespace
    while not (P[I] in [',', ' ', #0,']']) do
      Inc(I);
    SetString(Result, P, I);
    // skip whitespace
    while P[I] in [',', ' ',']'] do
      Inc(I);
    Inc(P, I);
  end;

begin
  SetOrdValue(Info, SetParam, 0);
  if Value = '' then
    Exit;

  SetValue := 0;
  P := PAnsiChar(Value);
  // skip leading bracket and whitespace
  while P^ in ['[',' '] do
    Inc(P);
  EnumInfo := GetTypeData(Info)^.CompType^;
  EnumName := NextWord(P);
  while EnumName <> '' do
  begin
    EnumValue := GetEnumValue(EnumInfo, EnumName);
    if EnumValue < 0 then
    begin
      SetOrdValue(Info, SetParam, 0);
      Exit;
    end;
    Include(TIntegerSet(SetValue), EnumValue);
    EnumName := NextWord(P);
  end;
  SetOrdValue(Info, SetParam, SetValue);
end;

Example usage:

var
  A: TAlignSet;
  S: AnsiString;
begin
  // set to string
  A := [alClient, alLeft, alTop];
  S := SetToString(TypeInfo(TAlignSet), A, True);
  ShowMessage(Format('%s ($%x)', [S, Byte(A)]));

  // string to set
  S := '[alNone, alRight, alCustom]';
  StringToSet(TypeInfo(TAlignSet), A, S);
  ShowMessage(Format('%s ($%x)', [SetToString(TypeInfo(TAlignSet), A, True), Byte(A)]));
end;

Update: I've changed the declarations of untyped parameters to const where they're not modified (originally, they were incorrectly declared as var). Thanks, Joe, for your comment!