Hi,

why is sizeof on object/class fields sometimes allowed and sometimes not?

type TTest = object
   f: integer;
   class procedure test;
end;
class procedure TTest.test;
begin
   writeln(sizeof(f));             // does not compile
   writeln(sizeof(TTest.f));  // compiles
end;

---

type TTest = class
   f: integer;
   class procedure test;
end;
class procedure TTest.test;
begin
   writeln(sizeof(f));             // does not compile
   writeln(sizeof(TTest.f));  // does not compile
end;

surely that should all be equal to sizeof(integer)

Bye,

Benito

In our previous episode, Benito van der Zander said:

For custom types that don't have a predefined IComparer instance, afaik you can define it yourself and set it in the TDictionary type.

Just search for I/Tcomparer in the generics.* sources.

I do have some example, but that is for the generic sort, not the dictionary:

program gensort2;
{$APPTYPE CONSOLE}
{$R *.res}
uses
  System.SysUtils,generics.collections,generics.defaults;
type
    TSomeRecord = record
                    angle:single;
                    angleasstring:string;
    end;
type
  TSomeRecordComparer1 = class(TComparer<TSomeRecord>)
  public
    function Compare(const Left, Right: TSomeRecord): Integer; override;
  end;
function TSomeRecordComparer1.Compare(const Left, Right: TSomeRecord):
Integer;
begin
  Result := round(left.angle - right.angle);
end;
var  some:array of TSomeRecord;
     i : integer;
     cmp : TSomeRecordComparer1;
begin
  cmp:=TSomeRecordComparer1.Create;
  setlength(some,6);
  some[0].angle:=100; some[1].angle:=25; some[2].angle:=270;
  some[3].angle:=90; some[4].angle:=15; some[5].angle:=300;
  for i := 0 to length(some)-1 do
    some[i].angleasstring:=FloatToStrF(some[i].angle,fffixed,8,4);
//  tarray.sort<tsomerecord>(some,cmp,3,3);  // partial sort
  tarray.sort<tsomerecord>(some,cmp);
  for i := 0 to length(some)-1 do
    writeln(some[i].angle:10:5,' ',some[i].angleasstring);
  readln;
end.

In our previous episode, Marco van de Voort said:

I accidentally replied the below post to the wrong thread, probably because they were both about operator definitions. Anyway the post was about the "why can't we define class operator for old fashion object type" thread, and how to customize generics.* classes in general:

Interestingly Delphi does not allow it either (though it fails with two different errors for the two variants (note: I only tested the class one)), so its behavior is the same as in FPC there. I personally would say that it should be allowed however... *shrugs*

Regards,
Sven