Class with builtin marshalling. Why are the field converters not working?

I have the following questions:

1. Should the marshalling be placed in a class helper instead? Or is it quite OK to place it "inside" the class?
2. Why are the field converters not working?

Using Delphi XE - consider this:

type
  TMyClass = Class
  public
    FaString : String;
    FaStringList : TStringList; 
    FMar : TJsonMarshal;
    procedure RegisterConverters;
    function Marshal : TJsonObject;  // should handle marshalling
  end;

RegisterConverters would look something like this.

procedure TMyClass.RegisterConverters;
begin
  // try and catch the marshaller itself.
  FMar.RegisterConverter(TJsonMarshal, 'FMar',
    function(Data : TObject; Field:String): TObject
    begin
      Exit(nil); // Since we cannot marshal it - and we dont need it anyways.
    end);
  // catch TStringList
  FMar.RegisterConverter(TStringList, 'FaStringList'开发者_C百科,
    function(Data: TObject; Field:String): TListOfStrings
    var
      i, count: integer;
    begin
      count := TStringList(Data).count;
      SetLength(Result, count);
      for i := 0 to count - 1 do
        Result[i] := TStringList(Data)[i];
    end);
end; 

And the Marshal method :

function TMyClass.Marshal: TJSONObject;
begin
  if FMar = nil then
    FMar := TJSONMarshal.Create(TJSONConverter.Create);
  try
    RegisterConverters;
    try
      Result := FMar.Marshal(Self) as TJSONObject;
    except
      Result := nil;
    end;
  finally
    FMar.Free;
  end;
end;

Then we can do this:

var
  aObj : TMyClass;
  ResultString : String;
begin
  aObj := TMyClass.Create;
  aObj.FaString := 'Test string';
  aObj.FaStringList := TStringList.Create;
  aObj.FaStringList.Add('stringliststring #1');
  aObj.FaStringList.Add('stringliststring #2');
  aObj.FaStringList.Add('stringliststring #3');
  aObj.FaStringList.Add('stringliststring #4');

  // StringList and JsonMarshal should be handled by converter
  ResultString := (aObj.Marshal).ToString;
end;

But I simply cannot get it working. Field Converters do not get triggered?

Am I doing something wrong here? Or should I look at my Delphi XE installation (perhaps it is pooched)?

When doing the marshal from "within" you have to set it up correctly :-)

procedure TMyClass.RegisterConverters;
begin
  // try and catch the marshaller itself.
  FMar.RegisterConverter(ClassType, 'FMar',
    function(Data : TObject; Field:String): TObject
    begin
      Exit(nil); // Since we cannot marshal it - and we dont need it anyways.
    end);
  // catch TStringList
  FMar.RegisterConverter(ClassType, 'FaStringList',
    function(Data: TObject; Field:String): TListOfStrings
    var
      i, count: integer;
    begin
      count := TStringList(Data).count;
      SetLength(Result, count);
      for i := 0 to count - 1 do
        Result[i] := TStringList(Data)[i];
    end);
end; 

The difference is using ClassType as the type in the call to RegisterConverter. Otherwise one cannot get to the specified field - I should have seen that !