Wednesday, October 17, 2007

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!
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