I've talked with some friends of mine about the use of Interface base classes
without reference counting in Delphi
like this
type
TNoRefCount = class(TObject, IUnknown)
protected
function QueryInterface(const IID:TGUID; out Obj):HResult; stdcall;
function _AddRef: Integer; stdcall;
function _Release: Integer; stdcall;
end;
function TNoRefCount.QueryInterface(const IID:TGUID; out Obj): HResult;
begin
if GetInterface(IID, Obj) then
Result := 0
else
Result := Windows.E_NoInterface;
end;
function TNoRefCount._AddRef: Integer;
begin
Result := -1
end;
function TNoRefCount._Release: Integer;
begin
Result := -1
end;
We are all experiencing the same kind of problems:
1) there's no easy way to obtain a TObject from an interface (whereas there's
no particular reason not to have it. A solution proposed was to implement an
AsObject method in all the interfaces used.
2) there's no FreeAndNil function that would free the interface and the object
instance.
It would be nice to be able to do something like this in an abstract factory:
var
MyRef: ISomeInterface;
begin
MyRef := SomeFactory.CreateObject as ISomeInterface;
try
...use MyRef...
finally
MyRef.AsObject.Free;
MyRef := nil;
end;
end;
Any Idea of a solution in free pascal?
Ciao, Dean
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