Как получить доступ к именам полей записи record? Как переименовать поля run-time?

type
defaults = record
     imlist, tileslist: array of string;
     filelist: array of array of string;
     dims: integer;
     weight: array of integer;
     maxtitle: byte;
     colour: array of word;
 end;
 
var
myRec: defaults;

procedure TForm1.Button33Click(Sender: TObject);
var
  rttiContext : TRttiContext;
  fld : TRttiField;
begin
  for fld in rttiContext.GetType(TypeInfo(defaults)).GetFields do
    Memo1.Lines.Add(fld.Name);
end;

var 
  i : Integer;
  fld : TRttiField;
 
  fld := rttiContext.GetType(TypeInfo(defaults)).GetField('dims');
  i := fld.GetValue(@myRec).AsInteger;
  fld.SetValue(@myRec, 42);

i := fld.GetValue(@myRec).AsInteger;

j := fld.GetValue(@myRec).AsString;

type
defaults = record
     imlist, tileslist: array of string;
     filelist: array of array of string;
     st : {short}string;
     dims: integer;
     weight: array of integer;
     maxtitle: byte;
     colour: array of word;
 end;
 
var
  myRec: defaults;
 
procedure TForm1.Button33Click(Sender: TObject);
var
  rttiContext : TRttiContext;
  fld : TRttiField;
 
  i : integer;
  j : string;
 
  rttiType: TRttiType;
  fields: TArray<TRttiField>;
begin
  myRec.dims := 10;
  myRec.st := 'just string';
 
  (*
  fld := rttiContext.GetType(TypeInfo(defaults)).GetField('dims');
  i := fld.GetValue(@myRec).AsInteger;
  fld.SetValue(@myRec, 42);
  *)
 
  fld := rttiContext.GetType(TypeInfo(defaults)).GetField('st');
  j := fld.GetValue(@myRec).AsString;
  ShowMessage(j);
  fld.SetValue(@myRec, '42');
end;

function TRttiField.GetValue(Instance: Pointer): TValue;
var
  ft: TRttiType;
begin
  ft := FieldType;
! if ft = nil then
!    raise InsufficientRtti;
  TValue.Make(PByte(Instance) + Offset, ft.Handle, Result);
end;

myrec= record
 arrfield: array [0..1] of byte;
 arrfield2: array [0..2] of integer;
end

type
dims = record
a,b,c: array [0..1] of byte;
end
 
myrec = record
field1: dims;
field2: shortstring;
end
 
var
defs: myrec;

rec2:=myrec.field1;