How to get the type information of a record by its pointer in Delphi XE?

Question

If I have a TList with many pointers of different record types in it, how do I access the values of the differents records within the TList?

Is there any way to get the record type or type information of those referenced recods?

I'm currently using Delphi XE.

Answer 1

Your different record types need a common header. You can then cast the list item pointers to that header type first to determine what record type to cast to next. For example:

type
  TRecType = (recA, recB, recC);

  PRecHeader = ^TRecHeader;
  TRecHeader = record
    RecType: TRecType;
    ...
  end;

  PRecordA = ^TRecordA;
  TRecordA = record
    Header: TRecHeader;
    IntValue: Integer;
  end;

  PRecordB = ^TRecordB;
  TRecordB = record
    Header: TRecHeader;
    StrValue: String;
  end;

  PRecordC = ^TRecordC;
  TRecordC = record
    Header: TRecHeader;
    DblValue: Double;
  end;

var
  PRec: Pointer;
begin
  PRec := List[Index];
  case PRecHeader(PRec)^.RecType of
    recA: use PRecordA(PRec)^.IntValue as needed ...
    recB: use PRecordB(PRec)^.StrValue as needed ...
    recC: use PRecordC(PRec)^.DblValue as needed ...
  end;
end;