IEnumVARIANT::Clone Method

ppEnum

On return, pointer to the location of the clone enumerator.

The return value obtained from the returned HRESULT is one of the following:

Using this function, a particular point in the enumeration sequence can be recorded, and then returned to at a later time. The returned enumerator is of the same actual interface as the one that is being cloned.

There is no guarantee that exactly the same set of variants will be enumerated the second time as was enumerated the first. Although an exact duplicate is desirable, the outcome depends on the collection being enumerated. You may find that it is impractical for some collections to maintain this condition (for example, an enumeration of the files in a directory).

The following code implements IEnumVariant::Clone. A complete example implementation of the IEnumVariant interface is available in the COM Fundamentals Lines sample (Enumvar.cpp).

STDMETHODIMP
CEnumVariant::Clone(IEnumVARIANT FAR* FAR* ppenum)
{
   CEnumVariant FAR* penum = NULL;
   HRESULT hr;

   if (ppenum == NULL)
      return E_INVALIDARG;

   *ppenum = NULL;

   hr = CEnumVariant::Create(m_psa, m_cElements, &penum);
   if (FAILED(hr))
      goto error;
   penum->AddRef();
   penum->m_lCurrent = m_lCurrent;

   *ppenum = penum;
   return NOERROR;

error:
   if (penum)
      penum->Release();
   return hr;
}

Reference