[fpc-pascal] TFPGObjectList error

[Michalis Kamburelis]

 2018-07-01 4:01 GMT+02:00 Vojtěch Čihák <vojtech.cihak at atlas.cz>:
> this seems to be misleading error message. TFPGObjectList works well for
> objects (classes). When I tried to push record to it, I got the same error
> message. TVec3 is not class, right?

Indeed, it's a misleading message. The message

   ...identifier idents no member "Free"

doesn't talk about the line

    list.Free;

(which is fine, "list" is an instance of a class). It talks most
likely about the "Free" call inside FGL implementation in

"""
procedure TFPGObjectList.Deref(Item: Pointer);
begin
  if FFreeObjects then
    T(Item^).Free;
end;
"""

If you look inside the FGL unit sources of your FPC version, you will
likely find this to be at line 992 :)

Short explanation:Since your TVec3 is probably not a class, you cannot
do "Free" on it.

The solution is to use TFPGList instead of TFPGObjectList. You should
also define an equality operator if TVec3 is a record. See e.g. my
example in https://castle-engine.io/modern_pascal_introduction.html#_operator_overloading
(scroll to the example with TMyRecordList).

Or you could use Generics.Collections unit with generic TList for
records. It by default compares records by comparing memory contents.

Regards,
Michalis