Generic functions for converting an enumeration to string and back

Question

I\'m trying to write functions that will convert an enumeration to string and back again.

ie:

TConversions = class
    strict private
    public
            


        

Answer 1

There seems to be no T:enum generic type constraint so I think the best you can do is check the type at runtime, something like this:

Edit: Based on David's comment, I've added the T: record constraint which can be used to constrain to value types (and rule out class types).

type
  TConversions = class
  public
    class function StringToEnumeration(const S: string): T;
    class function EnumerationToString(Value: T): string;
  end;

class function TConversions.EnumerationToString(Value: T): string;
var
  P: PTypeInfo;
begin
  P := PTypeInfo(TypeInfo(T));
  case P^.Kind of
    tkEnumeration:
      case GetTypeData(P)^.OrdType of
        otSByte, otUByte:
          Result := GetEnumName(P, PByte(@Value)^);
        otSWord, otUWord:
          Result := GetEnumName(P, PWord(@Value)^);
        otSLong, otULong:
          Result := GetEnumName(P, PCardinal(@Value)^);
      end;
    else
      raise EArgumentException.CreateFmt('Type %s is not enumeration', [P^.Name]);
  end;
end;

class function TConversions.StringToEnumeration(const S: string): T;
var
  P: PTypeInfo;
begin
  P := PTypeInfo(TypeInfo(T));
  case P^.Kind of
    tkEnumeration:
      case GetTypeData(P)^.OrdType of
        otSByte, otUByte:
          PByte(@Result)^ := GetEnumValue(P, S);
        otSWord, otUWord:
          PWord(@Result)^ := GetEnumValue(P, S);
        otSLong, otULong:
          PCardinal(@Result)^ := GetEnumValue(P, S);
      end;
    else
      raise EArgumentException.CreateFmt('Type %s is not enumeration', [P^.Name]);
  end;
end;