On Mon, Jun 10, 2019 at 3:31 PM Ryan Joseph <[email protected]> wrote:
> Sorry, if I dereference the size is still of TBase. I don’t think “result"
> is actually changing depending on the class type. This may have something
> to do with the way new works though. How can we fix this?
>
It's because Initialize isn't virtual (and can't be), meaning your code
really just creates a PBase and then hard-casts it to a PChild.
If you really want to use objects in that kind of way though, here's a
general example that works and doesn't leak memory:
program Test;
{$mode ObjFPC}
{$modeswitch AutoDeref}
type
PBase = ^TBase;
TBase = object
public
I: Int64;
constructor Initialize;
class function Create: PBase; static; inline;
procedure Free;
end;
constructor TBase.Initialize;
begin
WriteLn('Base!');
I := 12;
end;
class function TBase.Create: PBase;
begin
New(Result, Initialize);
end;
procedure TBase.Free;
begin
if Assigned(@Self) then begin
WriteLn('Size: ', SizeOf(Self));
FreeMem(@Self, SizeOf(Self));
end;
end;
type
PChild = ^TChild;
TChild = object(TBase)
public
S: String[5];
constructor Initialize;
class function Create: PChild; static; inline;
end;
constructor TChild.Initialize;
begin
inherited Initialize;
WriteLn('Child!');
S := 'hello';
end;
class function TChild.Create: PChild;
begin
New(Result, Initialize);
end;
var
PB: PBase;
PC: PChild;
begin
PB := TBase.Create;
WriteLn(PB.I);
PB.Free;
PC := TChild.Create;
WriteLn(PC.I);
WriteLn(PC.S);
PC.Free;
end.
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