Re: Design of array for holding interface pointer

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Wed, 18 Apr 2007 10:55:33 -0400

Message-ID:

<OffcemcgHHA.4260@TK2MSFTNGP03.phx.gbl>

aeshiels@gmail.com wrote:

Im writing a COM interface which will hold an array of my IItem3
interface pointers.

     std::vector < CAdapt< CComPtr<IItem3> > > m_aItems;

STDMETHODIMP CMyArray::putItem(IItem3 *pVal)
{

USES_CONVERSION;
CComPtr<IItem3> item3;
               HRESULT hr = pVal->QueryInterface(__uuidof(IItem3),
(void**)&item3);
               if(FAILED(hr))
    return hr;
m_aItems.push_back (item3);

return S_OK;
}

Your code is correct but way overcomplicated. Just do

m_aItems.push_back (pVal);

STDMETHODIMP CMyArray::getItem(IItem3 * * pVal)
{
if (m_aItems.size() == 0)
        return E_FAIL;

CComPtr <IItem3> item3 = ( CComPtr<IItem3> )m_aItems.front ();
               HRESULT hr = item3->QueryInterface(__uuidof(IItem3),
(void**)pVal);
               if(FAILED(hr))
    return hr;

Again, too complicated. Make it

HRESULT hr = m_aItems.front().m_T.CopyTo(pVal);

m_aItems.pop_back();

This looks suspicious. You are returning an element from the front of
the vector, but popping from the back. Is this really what you want?
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925