Re: [Boost-users] COM and boost::intrusive_ptr

Philipp Henkel wrote:

CComPtr-like usage: boost::intrusive_ptr<IVideo> video; someObject->QueryInterface(IID_IVideo,(void**)&video);

Is there a better way? How do you bring intrusive_ptr and QueryInterface together?

The technically correct way to use QueryInterface is to pass it the address of a void*: void* pv = 0; someObject->QueryInterface( IID_IVideo, &pv ); IVideo * pv2 = static_cast< IVideo* >( pv ); boost::intrusive_ptr<IVideo> video( pv2 ); pv2->Release(); The (void**) cast is too error-prone, even if you don't care about technicalities. This of course can be encapsulated in a function. template intrusive_ptr<Target> query_interface( Source ps, IID const & iid /* = __uuidof( Target ) */ ) { void* pv = 0; ps->QueryInterface( iid, &pv ); Target * pv2 = static_cast< Target* >( pv ); boost::intrusive_ptr<Target> target( pv2, false ); return target; } and then intrusive_ptr<IVideo> video = query_interface<IVideo>( someObject, IID_IVideo );