Hi,
A class (TFoo) implements an interface (IFoo), but my class has more methods and properties (in the eg below just one more method) that I need use.
Another object has a property of IFoo type.
So, I created a Foo and assigns my object property.
From this moment I can not longer release my Foo object, because the refcount.
See (attention in the comments below):
program p1;
{$ifdef FPC}
{$mode objfpc}{$H+}
{$else}
{$apptype console}
{$endif}
uses heaptrc, Classes, SysUtils;
type
IFoo = interface
['{F71A4131-E0A5-48CB-B563-7BBB079D1085}']
function GetInfo: string;
end;
TFoo = class(TInterfacedObject, IFoo)
private
FInfo: string;
protected
public
function GetInfo: string;
procedure SetInfo(const AValue: string);
end;
function TFoo.GetInfo: string;
begin
Result := FInfo;
end;
procedure TFoo.SetInfo(const AValue: string);
begin
FInfo := AValue;
end;
type
TObj = class(TObject)
public
Foo: IFoo;
end;
procedure Run;
var
f: TFoo; // << type is class, not interface
o: TObj;
begin
f := TFoo.Create;
f.SetInfo('foo');
o := TObj.Create;
o.Foo := f;
writeln(o.Foo.GetInfo);
o.Free;
// f.Free; // << I can't use it because it already was freed
end;
begin
Run;
writeln('Done');
end.BUT, if I create my TFoo without refcount should works, right? So, I change my class:
TFoo = class(TObject, IFoo)
private
FInfo: string;
protected
function QueryInterface(const iid : tguid;out obj) : longint;stdcall;
function _AddRef : longint;stdcall;
function _Release : longint;stdcall;
public
function GetInfo: string;
procedure SetInfo(const AValue: string);
end;
function TFoo.QueryInterface(const iid: TGuid; out obj): longint; stdcall;
begin
if GetInterface(iid,obj) then
Result := S_OK
else
Result:=longint(E_NOINTERFACE);
end;
function TFoo._AddRef: longint; stdcall;
begin
Result := -1;
end;
function TFoo._Release: longint; stdcall;
begin
Result := -1;
end;... but, does not work. In Delphi 7 yes, but no in FPC.
See this http://bugs.freepascal.org/view.php?id=15526
Do you think this is right?
Marcos Douglas